- preg_match: documentation ( source)
- print_r: documentation ( source)
<?php
$url = 'http://i0.letvimg.com/yunzhuanma/201411/02/48d4d1d7482144f5318b5a542048a84b/thumb/1_160_120.jpg';
preg_match('/.*\.letvimg\.com.*/', $url, $matches);
print_r($matches);