<?php
$cmd = array('system', 'passthru', 'exec', 'shell_exec', 'popen', 'proc_open', 'pcntl_exec');
$count = count($cmd);
for($x = 0; $x < $count; $x++)
   echo is_callable($cmd[$x]) ? "{$cmd[$x]} - Yes" . PHP_EOL : "{$cmd[$x]} - No" . PHP_EOL;
   echo function_exists($cmd[$x]) ? "{$cmd[$x]} - Yes" . PHP_EOL : "{$cmd[$x]} - No" . PHP_EOL;
?>