diff --git a/functionMap.php b/functionMap.php
index 47a4c29..3c5063a 100644
--- a/functionMap.php
+++ b/functionMap.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-$httpReturnType = 'array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error';
+$httpReturnType = 'array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error';
 
 if (file_exists(sprintf('%s/source/wordpress/wp-includes/Requests/Cookie/Jar.php', __DIR__))) {
     $httpReturnType = 'array{headers: \Requests_Utility_CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error';
@@ -177,6 +177,15 @@
     'WP_Widget::form' => [null, 'instance' => 'T'],
     'WP_Widget::update' => [null, 'new_instance' => 'T', 'old_instance' => 'T'],
     'WP_Widget::widget' => [null, 'instance' => 'T', 'args' => 'array{name:string,id:string,description:string,class:string,before_widget:string,after_widget:string,before_title:string,after_title:string,before_sidebar:string,after_sidebar:string,show_in_rest:boolean,widget_id:string,widget_name:string}'],
+    'get_approved_comments' => ["(\$args is array{count: true} ? int : (\$args is array{fields: 'ids'} ?  array<int, int> : array<int, \WP_Comment>))"],
+    'get_posts' => ["(\$args is array{fields: 'id=>parent'|'ids'} ? array<int, int> : array<int, \WP_Post>)"],
+    'get_sites' => ["(\$args is array{count: true} ? int : (\$args is array{fields: 'ids'} ?  array<int, int> : array<int, \WP_Site>))"],
+    'get_tags' =>  ["(\$args is array{fields: 'count'} ? numeric-string : (\$args is array{fields: 'names'|'slugs'} ? list<string> : (\$args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : (\$args is array{fields: 'id=>parent'} ? array<int, int> : (\$args is array{fields: 'ids'|'tt_ids'} ? list<int> : array<int, \WP_Term>)))))|\WP_Error"],
+    'get_terms' => ["(\$args is array{fields: 'count'} ? numeric-string : (\$args is array{fields: 'names'|'slugs'} ? list<string> : (\$args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : (\$args is array{fields: 'id=>parent'} ? array<int, int> : (\$args is array{fields: 'ids'|'tt_ids'} ? list<int> : array<int, \WP_Term>)))))|\WP_Error"],
+    'wp_get_post_categories' => ["(\$post_id is 0 ? array{} : ((\$args is array{fields: 'names'|'slugs'} ? list<string> : (\$args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : (\$args is array{fields: 'id=>parent'} ? array<int, int> : (\$args is array{fields: 'all'|'all_with_object_id'} ? array<int, \WP_Term> : (\$args is array{fields: 'count'} ? numeric-string : list<int>)))))|\WP_Error))"],
+    'wp_get_post_tags' => ["(\$post_id is 0 ? array{} : ((\$args is array{fields: 'names'|'slugs'} ? list<string> : (\$args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : (\$args is array{fields: 'id=>parent'} ? array<int, int> : (\$args is array{fields: 'ids'|'tt_ids'} ? list<int> : (\$args is array{fields: 'count'} ? numeric-string : array<int, \WP_Term>)))))|\WP_Error))"],
+    'wp_get_post_terms' => ["(\$post_id is 0 ? array{} : (\$taxonomy is empty ? array{} : ((\$args is array{fields: 'names'|'slugs'} ? list<string> : (\$args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : (\$args is array{fields: 'id=>parent'} ? array<int, int> : (\$args is array{fields: 'ids'|'tt_ids'} ? list<int> : (\$args is array{fields: 'count'} ? numeric-string : array<int, \WP_Term>)))))|\WP_Error)))"],
+    'wp_get_object_terms' => ["(\$object_ids is empty ? array{} : (\$taxonomies is empty ? array{} : ((\$args is array{fields: 'names'|'slugs'} ? list<string> : (\$args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : (\$args is array{fields: 'id=>parent'} ? array<int, int> : (\$args is array{fields: 'ids'|'tt_ids'} ? list<int> : (\$args is array{fields: 'count'} ? numeric-string : array<int, \WP_Term>)))))|\WP_Error)))"],
     'wp_parse_list' => ['($input_list is array ? array<scalar> : list<string>)'],
     'wp_parse_str' => [null, '@phpstan-param-out' => 'array<int|string, array|string> $result'],
     'size_format' => ["(\$bytes is not numeric ? false : (\$bytes is negative-int|'0' ? false : string))"],
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index e4906a4..4af178a 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -50,6 +50,9 @@
     <rule ref="WordPress.WP.GlobalVariablesOverride">
         <exclude-pattern>tests/</exclude-pattern>
     </rule>
+    <rule ref="NeutronStandard.Functions.LongFunction.LongFunction">
+        <exclude-pattern>tests/TypeInferenceTest.php</exclude-pattern>
+    </rule>
     <rule ref="NeutronStandard.Functions.TypeHint.UnusedReturnType">
         <exclude-pattern>tests/TypeInferenceTest.php</exclude-pattern>
     </rule>
diff --git a/tests/TypeInferenceTest.php b/tests/TypeInferenceTest.php
index 1e7f142..bdf00c8 100644
--- a/tests/TypeInferenceTest.php
+++ b/tests/TypeInferenceTest.php
@@ -12,6 +12,7 @@ public function dataFileAsserts(): iterable
         yield from $this->gatherAssertTypes(__DIR__ . '/data/_get_list_table.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/current_time.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/echo_parameter.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/get_approved_comments.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_attachment_taxonomies.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_bookmark.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_categories.php');
@@ -22,9 +23,13 @@ public function dataFileAsserts(): iterable
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_post.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_post_stati.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_post_types.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/get_posts.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_page_by_path.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_permalink.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/get_sites.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/get_tags.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_term_by.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/get_terms.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_taxonomies.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_term.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/get_taxonomies_for_attachments.php');
@@ -40,6 +45,10 @@ public function dataFileAsserts(): iterable
         yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_error_parameter.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_generate_tag_cloud.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_get_archives.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_get_post_categories.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_get_post_tags.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_get_post_terms.php');
+        yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_get_object_terms.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_is_numeric_array.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_list_bookmarks.php');
         yield from $this->gatherAssertTypes(__DIR__ . '/data/wp_list_categories.php');
diff --git a/tests/data/get_approved_comments.php b/tests/data/get_approved_comments.php
new file mode 100644
index 0000000..28ab1e3
--- /dev/null
+++ b/tests/data/get_approved_comments.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function get_approved_comments;
+use function PHPStan\Testing\assertType;
+
+assertType('array<int, WP_Comment>', get_approved_comments(1));
+
+assertType('int', get_approved_comments(1, ['count' => true]));
+
+assertType('int', get_approved_comments(1, ['count' => true,'fields' => 'ids']));
+
+assertType('array<int, WP_Comment>', get_approved_comments(1, ['count' => false]));
+
+assertType('array<int, int>', get_approved_comments(1, ['fields' => 'ids']));
+
+assertType('array<int, int>', get_approved_comments(1, ['count' => false, 'fields' => 'ids']));
diff --git a/tests/data/get_posts.php b/tests/data/get_posts.php
new file mode 100644
index 0000000..7cbb151
--- /dev/null
+++ b/tests/data/get_posts.php
@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function get_posts;
+use function PHPStan\Testing\assertType;
+
+assertType('array<int, WP_Post>', get_posts());
+assertType('array<int, WP_Post>', get_posts(['key' => 'value']));
+assertType('array<int, WP_Post>', get_posts(['fields' => '']));
+assertType('array<int, int>', get_posts(['fields' => 'ids']));
+assertType('array<int, int>', get_posts(['fields' => 'id=>parent']));
+assertType('array<int, WP_Post>', get_posts(['fields' => 'Hello']));
+
+// Nonconstant array
+assertType('array<int, int|WP_Post>', get_posts((array)$_GET['array']));
+
+// Unions
+$union = $_GET['foo'] ? ['key' => 'value'] : ['some' => 'thing'];
+assertType('array<int, WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? ['key' => 'value'] : ['fields' => 'ids'];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? ['key' => 'value'] : ['fields' => ''];
+assertType('array<int, WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? ['key' => 'value'] : ['fields' => 'id=>parent'];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? ['fields' => ''] : ['fields' => 'ids'];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? ['fields' => ''] : ['fields' => 'id=>parent'];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? ['fields' => 'ids'] : ['fields' => 'id=>parent'];
+assertType('array<int, int>', get_posts($union));
+
+$union = $_GET['foo'] ? (array)$_GET['array'] : ['fields' => ''];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? (array)$_GET['array'] : ['fields' => 'ids'];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? (array)$_GET['array'] : ['fields' => 'id=>parent'];
+assertType('array<int, int|WP_Post>', get_posts($union));
+
+$union = $_GET['foo'] ? (string)$_GET['string'] : '';
+assertType('array<int, int|WP_Post>', get_posts(['fields' => $union]));
+
+$union = $_GET['foo'] ? (string)$_GET['string'] : 'ids';
+assertType('array<int, int|WP_Post>', get_posts(['fields' => $union]));
+
+$union = $_GET['foo'] ? (string)$_GET['string'] : 'id=>parent';
+assertType('array<int, int|WP_Post>', get_posts(['fields' => $union]));
+
+$union = $_GET['foo'] ? (string)$_GET['string'] : 'fields';
+assertType('array<int, WP_Post>', get_posts([$union => '']));
+
+$union = $_GET['foo'] ? (string)$_GET['string'] : 'fields';
+assertType('array<int, int|WP_Post>', get_posts([$union => 'ids']));
+
+$union = $_GET['foo'] ? (string)$_GET['string'] : 'fields';
+assertType('array<int, int|WP_Post>', get_posts([$union => 'id=>parent']));
diff --git a/tests/data/get_sites.php b/tests/data/get_sites.php
new file mode 100644
index 0000000..a4a809b
--- /dev/null
+++ b/tests/data/get_sites.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function get_sites;
+use function PHPStan\Testing\assertType;
+
+// Default parameter
+assertType('array<int, WP_Site>', get_sites());
+assertType('array<int, WP_Site>', get_sites([]));
+
+// Non constant array parameter
+/** @var array<int|string,mixed> $value */
+$value = $_GET['foo'];
+assertType('array<int, int|WP_Site>|int', get_sites($value));
+
+// Array parameter with explicit fields value and default count value.
+assertType('array<int, int>', get_sites(['fields' => 'ids']));
+assertType('array<int, WP_Site>', get_sites(['fields' => '']));
+assertType('array<int, WP_Site>', get_sites(['fields' => 'nonEmptyString']));
+
+// Array parameter with count set to true.
+assertType('int', get_sites(['count' => true]));
+assertType('int', get_sites(['fields' => '', 'count' => true]));
+assertType('int', get_sites(['fields' => 'ids', 'count' => true]));
+assertType('int', get_sites(['fields' => 'nonEmptyString', 'count' => true]));
+
+// Array parameter with count set to false.
+assertType('array<int, WP_Site>', get_sites(['count' => false]));
+assertType('array<int, WP_Site>', get_sites(['fields' => '', 'count' => false]));
+assertType('array<int, int>', get_sites(['fields' => 'ids', 'count' => false]));
+assertType('array<int, WP_Site>', get_sites(['fields' => 'nonEmptyString', 'count' => false]));
diff --git a/tests/data/get_tags.php b/tests/data/get_tags.php
new file mode 100644
index 0000000..85a74dd
--- /dev/null
+++ b/tests/data/get_tags.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function get_tags;
+use function PHPStan\Testing\assertType;
+
+// Default argument values (fields => all)
+assertType('array<int, WP_Term>|WP_Error', get_tags());
+assertType('array<int, WP_Term>|WP_Error', get_tags([]));
+
+// Requesting a count
+assertType('numeric-string|WP_Error', get_tags(['fields' => 'count']));
+assertType('numeric-string|WP_Error', get_tags(['foo' => 'bar','fields' => 'count']));
+
+// Requesting names or slugs
+assertType('list<string>|WP_Error', get_tags(['fields' => 'names']));
+assertType('list<string>|WP_Error', get_tags(['fields' => 'slugs']));
+assertType('array<int, string>|WP_Error', get_tags(['fields' => 'id=>name']));
+assertType('array<int, string>|WP_Error', get_tags(['fields' => 'id=>slug']));
+
+// Requesting IDs
+assertType('list<int>|WP_Error', get_tags(['fields' => 'ids']));
+assertType('list<int>|WP_Error', get_tags(['fields' => 'tt_ids']));
+
+// Requesting parent IDs
+assertType('array<int, int>|WP_Error', get_tags(['fields' => 'id=>parent']));
+
+// Requesting objects
+assertType('array<int, WP_Term>|WP_Error', get_tags(['fields' => 'all']));
+assertType('array<int, WP_Term>|WP_Error', get_tags(['fields' => 'all_with_object_id']));
+assertType('array<int, WP_Term>|WP_Error', get_tags(['fields' => 'foo']));
+
+// Unknown fields value
+assertType('array<int, int|string|WP_Term>|numeric-string|WP_Error', get_tags(['fields' => (string)$_GET['fields']]));
diff --git a/tests/data/get_terms.php b/tests/data/get_terms.php
new file mode 100644
index 0000000..dd83fb2
--- /dev/null
+++ b/tests/data/get_terms.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function get_terms;
+use function PHPStan\Testing\assertType;
+
+// Default argument values (fields => all)
+assertType('array<int, WP_Term>|WP_Error', get_terms());
+assertType('array<int, WP_Term>|WP_Error', get_terms([]));
+
+// Requesting a count
+assertType('numeric-string|WP_Error', get_terms(['fields' => 'count']));
+assertType('numeric-string|WP_Error', get_terms(['foo' => 'bar','fields' => 'count']));
+
+// Requesting names or slugs
+assertType('list<string>|WP_Error', get_terms(['fields' => 'names']));
+assertType('list<string>|WP_Error', get_terms(['fields' => 'slugs']));
+assertType('array<int, string>|WP_Error', get_terms(['fields' => 'id=>name']));
+assertType('array<int, string>|WP_Error', get_terms(['fields' => 'id=>slug']));
+
+// Requesting IDs
+assertType('list<int>|WP_Error', get_terms(['fields' => 'ids']));
+assertType('list<int>|WP_Error', get_terms(['fields' => 'tt_ids']));
+
+// Requesting parent IDs
+assertType('array<int, int>|WP_Error', get_terms(['fields' => 'id=>parent']));
+
+// Requesting objects
+assertType('array<int, WP_Term>|WP_Error', get_terms(['fields' => 'all']));
+assertType('array<int, WP_Term>|WP_Error', get_terms(['fields' => 'all_with_object_id']));
+assertType('array<int, WP_Term>|WP_Error', get_terms(['fields' => 'foo']));
+
+// Unknown fields value
+assertType('array<int, int|string|WP_Term>|numeric-string|WP_Error', get_terms(['fields' => (string)$_GET['fields']]));
diff --git a/tests/data/wp_get_object_terms.php b/tests/data/wp_get_object_terms.php
new file mode 100644
index 0000000..990fb9a
--- /dev/null
+++ b/tests/data/wp_get_object_terms.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function wp_get_object_terms;
+use function PHPStan\Testing\assertType;
+
+$objectIDs = 123;
+$taxonomies = 'category';
+
+// Default argument values (fields => all)
+assertType('array<int, WP_Term>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies));
+assertType('array<int, WP_Term>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, []));
+
+// Empty $object_ids or $taxonomies
+assertType('array{}', wp_get_object_terms(0, $taxonomies, ['fields' => 'count']));
+assertType('array{}', wp_get_object_terms([], $taxonomies));
+assertType('array{}', wp_get_object_terms($objectIDs, ''));
+assertType('array{}', wp_get_object_terms($objectIDs, []));
+
+// Requesting names or slugs
+assertType('list<string>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'names']));
+assertType('list<string>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'slugs']));
+assertType('array<int, string>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'id=>name']));
+assertType('array<int, string>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'id=>slug']));
+
+// Requesting IDs
+assertType('list<int>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'ids']));
+assertType('list<int>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'tt_ids']));
+
+// Requesting parent IDs
+assertType('array<int, int>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'id=>parent']));
+
+// Requesting objects
+assertType('array<int, WP_Term>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'all']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'all_with_object_id']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'foo']));
+
+// Requesting a count
+assertType('numeric-string|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => 'count']));
+
+// Unknown fields value
+assertType('array<int, int|string|WP_Term>|numeric-string|WP_Error', wp_get_object_terms($objectIDs, $taxonomies, ['fields' => (string)$_GET['fields']]));
diff --git a/tests/data/wp_get_post_categories.php b/tests/data/wp_get_post_categories.php
new file mode 100644
index 0000000..43827eb
--- /dev/null
+++ b/tests/data/wp_get_post_categories.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function wp_get_post_categories;
+use function PHPStan\Testing\assertType;
+
+$postID = 123;
+
+// Default argument values (fields => ids)
+assertType('list<int>|WP_Error', wp_get_post_categories($postID));
+assertType('list<int>|WP_Error', wp_get_post_categories($postID, []));
+
+// Empty $post_id
+assertType('array{}', wp_get_post_categories(0));
+
+// Requesting names or slugs
+assertType('list<string>|WP_Error', wp_get_post_categories($postID, ['fields' => 'names']));
+assertType('list<string>|WP_Error', wp_get_post_categories($postID, ['fields' => 'slugs']));
+assertType('array<int, string>|WP_Error', wp_get_post_categories($postID, ['fields' => 'id=>name']));
+assertType('array<int, string>|WP_Error', wp_get_post_categories($postID, ['fields' => 'id=>slug']));
+
+// Requesting IDs
+assertType('list<int>|WP_Error', wp_get_post_categories($postID, ['fields' => 'ids']));
+assertType('list<int>|WP_Error', wp_get_post_categories($postID, ['fields' => 'tt_ids']));
+
+// Requesting parent IDs
+assertType('array<int, int>|WP_Error', wp_get_post_categories($postID, ['fields' => 'id=>parent']));
+
+// Requesting objects
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_categories($postID, ['fields' => 'all']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_categories($postID, ['fields' => 'all_with_object_id']));
+assertType('list<int>|WP_Error', wp_get_post_categories($postID, ['fields' => 'foo']));
+
+// Requesting a count
+assertType('numeric-string|WP_Error', wp_get_post_categories($postID, ['fields' => 'count']));
+
+// Unknown fields value
+assertType('array<int, int|string|WP_Term>|numeric-string|WP_Error', wp_get_post_categories($postID, ['fields' => (string)$_GET['fields']]));
diff --git a/tests/data/wp_get_post_tags.php b/tests/data/wp_get_post_tags.php
new file mode 100644
index 0000000..d9ab377
--- /dev/null
+++ b/tests/data/wp_get_post_tags.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function wp_get_post_tags;
+use function PHPStan\Testing\assertType;
+
+$postID = 123;
+
+// Default argument values (fields => all)
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_tags($postID));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_tags($postID, []));
+
+// Empty $post_id
+assertType('array{}', wp_get_post_tags(0));
+
+// Requesting names or slugs
+assertType('list<string>|WP_Error', wp_get_post_tags($postID, ['fields' => 'names']));
+assertType('list<string>|WP_Error', wp_get_post_tags($postID, ['fields' => 'slugs']));
+assertType('array<int, string>|WP_Error', wp_get_post_tags($postID, ['fields' => 'id=>name']));
+assertType('array<int, string>|WP_Error', wp_get_post_tags($postID, ['fields' => 'id=>slug']));
+
+// Requesting IDs
+assertType('list<int>|WP_Error', wp_get_post_tags($postID, ['fields' => 'ids']));
+assertType('list<int>|WP_Error', wp_get_post_tags($postID, ['fields' => 'tt_ids']));
+
+// Requesting parent IDs
+assertType('array<int, int>|WP_Error', wp_get_post_tags($postID, ['fields' => 'id=>parent']));
+
+// Requesting objects
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_tags($postID, ['fields' => 'all']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_tags($postID, ['fields' => 'all_with_object_id']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_tags($postID, ['fields' => 'foo']));
+
+// Requesting a count
+assertType('numeric-string|WP_Error', wp_get_post_tags($postID, ['fields' => 'count']));
+
+// Unknown fields value
+assertType('array<int, int|string|WP_Term>|numeric-string|WP_Error', wp_get_post_tags($postID, ['fields' => (string)$_GET['fields']]));
diff --git a/tests/data/wp_get_post_terms.php b/tests/data/wp_get_post_terms.php
new file mode 100644
index 0000000..7617280
--- /dev/null
+++ b/tests/data/wp_get_post_terms.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpStubs\WordPress\Core\Tests;
+
+use function wp_get_post_terms;
+use function PHPStan\Testing\assertType;
+
+$postID = 123;
+$taxonomy = 'post_tag';
+
+// Default argument values (fields => all)
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_terms($postID, $taxonomy));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_terms($postID, $taxonomy, []));
+
+// Empty $post_id or $taxonomy
+assertType('array{}', wp_get_post_terms(0, $taxonomy));
+assertType('array{}', wp_get_post_terms($postID, ''));
+assertType('array{}', wp_get_post_terms($postID, []));
+
+// Requesting names or slugs
+assertType('list<string>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'names']));
+assertType('list<string>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'slugs']));
+assertType('array<int, string>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'id=>name']));
+assertType('array<int, string>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'id=>slug']));
+
+// Requesting IDs
+assertType('list<int>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'ids']));
+assertType('list<int>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'tt_ids']));
+
+// Requesting parent IDs
+assertType('array<int, int>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'id=>parent']));
+
+// Requesting objects
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'all']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'all_with_object_id']));
+assertType('array<int, WP_Term>|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'foo']));
+
+// Requesting a count
+assertType('numeric-string|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => 'count']));
+
+// Unknown fields value
+assertType('array<int, int|string|WP_Term>|numeric-string|WP_Error', wp_get_post_terms($postID, $taxonomy, ['fields' => (string)$_GET['fields']]));
diff --git a/wordpress-stubs.php b/wordpress-stubs.php
index 0f35167..6843940 100644
--- a/wordpress-stubs.php
+++ b/wordpress-stubs.php
@@ -41475,7 +41475,7 @@ class WP_Http
          *   filename?: string,
          *   limit_response_size?: int,
          * } $args
-         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
          */
         public function request($url, $args = array())
         {
@@ -41546,7 +41546,7 @@ public function _get_first_available_transport($args, $url = \null)
          * @param string|array $args Optional. Override the defaults.
          * @return array|WP_Error Array containing 'headers', 'body', 'response', 'cookies', 'filename'.
          *                        A WP_Error instance upon error. See WP_Http::response() for details.
-         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
          */
         public function post($url, $args = array())
         {
@@ -41562,7 +41562,7 @@ public function post($url, $args = array())
          * @param string|array $args Optional. Override the defaults.
          * @return array|WP_Error Array containing 'headers', 'body', 'response', 'cookies', 'filename'.
          *                        A WP_Error instance upon error. See WP_Http::response() for details.
-         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
          */
         public function get($url, $args = array())
         {
@@ -41578,7 +41578,7 @@ public function get($url, $args = array())
          * @param string|array $args Optional. Override the defaults.
          * @return array|WP_Error Array containing 'headers', 'body', 'response', 'cookies', 'filename'.
          *                        A WP_Error instance upon error. See WP_Http::response() for details.
-         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+         * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
          */
         public function head($url, $args = array())
         {
@@ -102740,6 +102740,7 @@ function sanitize_category_field($field, $value, $cat_id, $context)
      * @phpstan-param array{
      *   taxonomy?: string,
      * } $args
+     * @phpstan-return ($args is array{fields: 'count'} ? numeric-string : ($args is array{fields: 'names'|'slugs'} ? list<string> : ($args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : ($args is array{fields: 'id=>parent'} ? array<int, int> : ($args is array{fields: 'ids'|'tt_ids'} ? list<int> : array<int, \WP_Term>)))))|\WP_Error
      */
     function get_tags($args = '')
     {
@@ -104032,6 +104033,7 @@ function check_comment($author, $email, $url, $comment, $user_ip, $user_agent, $
      *   update_comment_meta_cache?: bool,
      *   update_comment_post_cache?: bool,
      * } $args
+     * @phpstan-return ($args is array{count: true} ? int : ($args is array{fields: 'ids'} ?  array<int, int> : array<int, \WP_Comment>))
      */
     function get_approved_comments($post_id, $args = array())
     {
@@ -118457,7 +118459,7 @@ function _wp_http_get_object()
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_safe_remote_request($url, $args = array())
     {
@@ -118500,7 +118502,7 @@ function wp_safe_remote_request($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_safe_remote_get($url, $args = array())
     {
@@ -118543,7 +118545,7 @@ function wp_safe_remote_get($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_safe_remote_post($url, $args = array())
     {
@@ -118586,7 +118588,7 @@ function wp_safe_remote_post($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_safe_remote_head($url, $args = array())
     {
@@ -118650,7 +118652,7 @@ function wp_safe_remote_head($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_remote_request($url, $args = array())
     {
@@ -118686,7 +118688,7 @@ function wp_remote_request($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_remote_get($url, $args = array())
     {
@@ -118722,7 +118724,7 @@ function wp_remote_get($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_remote_post($url, $args = array())
     {
@@ -118758,7 +118760,7 @@ function wp_remote_post($url, $args = array())
      *   filename?: string,
      *   limit_response_size?: int,
      * } $args See WP_Http::request()
-     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int,message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
+     * @phpstan-return array{headers: \WpOrg\Requests\Utility\CaseInsensitiveDictionary, body: string, response: array{code: int, message: string}, cookies: array<int, \WP_Http_Cookie>, filename: string|null, http_response: \WP_HTTP_Requests_Response}|\WP_Error
      */
     function wp_remote_head($url, $args = array())
     {
@@ -128249,6 +128251,7 @@ function update_sitemeta_cache($site_ids)
      *   meta_type_key?: string,
      *   meta_query?: array,
      * } $args See WP_Site_Query::__construct()
+     * @phpstan-return ($args is array{count: true} ? int : ($args is array{fields: 'ids'} ?  array<int, int> : array<int, \WP_Site>))
      */
     function get_sites($args = array())
     {
@@ -133662,6 +133665,7 @@ function is_post_publicly_viewable($post = \null)
      *   w?: int,
      *   year?: int,
      * } $args
+     * @phpstan-return ($args is array{fields: 'id=>parent'|'ids'} ? array<int, int> : array<int, \WP_Post>)
      */
     function get_posts($args = \null)
     {
@@ -134176,6 +134180,7 @@ function wp_untrash_post_comments($post = \null)
      *   meta_type_key?: string,
      *   meta_query?: array,
      * } $args See WP_Term_Query::__construct()
+     * @phpstan-return ($post_id is 0 ? array{} : (($args is array{fields: 'names'|'slugs'} ? list<string> : ($args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : ($args is array{fields: 'id=>parent'} ? array<int, int> : ($args is array{fields: 'all'|'all_with_object_id'} ? array<int, \WP_Term> : ($args is array{fields: 'count'} ? numeric-string : list<int>)))))|\WP_Error))
      */
     function wp_get_post_categories($post_id = 0, $args = array())
     {
@@ -134231,6 +134236,7 @@ function wp_get_post_categories($post_id = 0, $args = array())
      *   meta_type_key?: string,
      *   meta_query?: array,
      * } $args See WP_Term_Query::__construct()
+     * @phpstan-return ($post_id is 0 ? array{} : (($args is array{fields: 'names'|'slugs'} ? list<string> : ($args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : ($args is array{fields: 'id=>parent'} ? array<int, int> : ($args is array{fields: 'ids'|'tt_ids'} ? list<int> : ($args is array{fields: 'count'} ? numeric-string : array<int, \WP_Term>)))))|\WP_Error))
      */
     function wp_get_post_tags($post_id = 0, $args = array())
     {
@@ -134288,6 +134294,7 @@ function wp_get_post_tags($post_id = 0, $args = array())
      *   meta_type_key?: string,
      *   meta_query?: array,
      * } $args
+     * @phpstan-return ($post_id is 0 ? array{} : ($taxonomy is empty ? array{} : (($args is array{fields: 'names'|'slugs'} ? list<string> : ($args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : ($args is array{fields: 'id=>parent'} ? array<int, int> : ($args is array{fields: 'ids'|'tt_ids'} ? list<int> : ($args is array{fields: 'count'} ? numeric-string : array<int, \WP_Term>)))))|\WP_Error)))
      */
     function wp_get_post_terms($post_id = 0, $taxonomy = 'post_tag', $args = array())
     {
@@ -140389,6 +140396,7 @@ function get_term_to_edit($id, $taxonomy)
      *   meta_type_key?: string,
      *   meta_query?: array,
      * } $args See WP_Term_Query::__construct()
+     * @phpstan-return ($args is array{fields: 'count'} ? numeric-string : ($args is array{fields: 'names'|'slugs'} ? list<string> : ($args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : ($args is array{fields: 'id=>parent'} ? array<int, int> : ($args is array{fields: 'ids'|'tt_ids'} ? list<int> : array<int, \WP_Term>)))))|\WP_Error
      */
     function get_terms($args = array(), $deprecated = '')
     {
@@ -140812,6 +140820,7 @@ function wp_delete_category($cat_id)
      *   meta_type_key?: string,
      *   meta_query?: array,
      * } $args See WP_Term_Query::__construct()
+     * @phpstan-return ($object_ids is empty ? array{} : ($taxonomies is empty ? array{} : (($args is array{fields: 'names'|'slugs'} ? list<string> : ($args is array{fields: 'id=>name'|'id=>slug'} ? array<int, string> : ($args is array{fields: 'id=>parent'} ? array<int, int> : ($args is array{fields: 'ids'|'tt_ids'} ? list<int> : ($args is array{fields: 'count'} ? numeric-string : array<int, \WP_Term>)))))|\WP_Error)))
      */
     function wp_get_object_terms($object_ids, $taxonomies, $args = array())
     {