Why don't POSIX functions work?

Question

PHP

I have Bitrix site management on VDS. Faced the following problem, POSIX functions do not work. Although they should work by default.
Yes it had problems with pcntl, but after installing certain packages, everything works fine.
But if you try to use POSIX commands, even through the PHP command line in the admin panel, even through running the script, an error is generated Call to undefined function posix_* (*-any posix function).
I tried to install the package yum -y install php-process , it did not help, the error remained the same.
Help out.

Answer 1

The solution turned out to be very simple:
Download PHP from the official site ( php.net/downloads.php)
Like this:
(eg $ wget br.php.net/get/php-5.3.15.tar.gz/from/this/mirror)
Attention! The version of the downloaded PHP must match yours, otherwise nothing will work!
-> sudo su
-> tar -zxvf php-5.3.15.tar.gz
-> cd php-5.3.15/ext/posix/
-> phpize && ./configure && make install
-> echo "extension=posix.so " >> /etc/php.ini
-> apachectl restart