Description:
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in php.ini,popen function is in disable functions:
disable_functions => passthru,system,popen,chroot,escapeshellcmd,proc_get_status => passthru,system,popen,chroot,escapeshellcmd,proc_get_status

function_exists('popen') return false,but when call popen, php only give a notice,but not throw a fatal error。

Test script:
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<?php
error_reporting(E_ALL);
ini_set('display_errors','on');
var_dump(function_exists('popen'));//false
$handle = popen("/bin/ls", "r");//null Warning: popen() has been disabled for security reasons in
var_dump($handle);
echo gettype($handle);

Expected result:
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when popen function is called,php should throw a fatal error。