Thanks for PR but hex2bin() is supported only 5.4+. What is the reason for use it instead of unpack()?

unpack() return the value as "Array"
http://php.net/manual/en/function.unpack.php

I can get only "Array" as String from following code,
echo unpack('H', '89504e470d0a1a0a0000000d494844520000010000000100010300000066bc3a2500000003504c5445000000a77a3dda0000000174524e530040e6d8660000001f494441541819edc1010d000000c220fba77e0e37600000000000000000e70221000001f5a2bd040000000049454e44ae426082');

But I try this code only over php 7.0. Is it a version issue?

Yes, version problem. I'm running 5.6 / 7 and it is OK but we are supporting now 5.2 that is a reason for old Array() usage etc. As I see statistics e.g: https://seld.be/notes/php-versions-stats-2017-1-edition We can leave support for less than 5.4. I will discuss it with my colleagues