Please note that when saving using an FTP host, an additional stream context must be passed through telling PHP to overwrite the file.
<?php
/* set the FTP hostname */
$user = "test";
$pass = "myFTP";
$host = "example.com";
$file = "test.txt";
$hostname = $user . ":" . $pass . "@" . $host . "/" . $file;
/* the file content */
$content = "this is just a test.";
/* create a stream context telling PHP to overwrite the file */
$options = array('ftp' => array('overwrite' => true));
$stream = stream_context_create($options);
/* and finally, put the contents */
file_put_contents($hostname, $content, 0, $stream);
?>