- var_dump: documentation ( source)
- str_replace: documentation ( source)
<?php
$s="sasas @prashnthm sdhjds @medonthi http://t.co/s3tZXim14e";
$url="http://t.co/s3tZXim14e";
$durl="pic.twitter.com/s3tZXim14e";
$data=str_replace($url,$durl,$s);
var_dump($data);
?>