shell_exec

This function is identical to the backtick operator.

The command that will be executed.

The output from the executed command or NULL if an error occurred or the command produces no output.

Note:

This function can return NULL both when an error occurs or the program produces no output. It is not possible to detect execution failures using this function. exec() should be used when access to the program exit code is required.

This function is disabled when PHP is running in safe mode.

<?php
$output = shell_exec('ls -lart');
echo "<pre>$output</pre>";
?>

exec() -

escapeshellcmd() -