The PHP execution operator consists of backticks (``) and is used to run shell commands. The output of the command will be returned, and may, therefore, be stored in a variable.
// List files
$output = `ls`;
echo "<pre>$output</pre>";
Note that the execute operator and [shell_exec()](<http://php.net/manual/en/function.shell-exec.php>)
will give the same result.