$re = '/\.\.\/img\/([\w.]+)/';
$str = 'background:#eeeded url(../img/bg.jpg)
background:#eeeded url(../img/bg1.jpg)
background:#eeeded url(../img/bg2.jpg)
<img src="../img/logo.jpg">
<img src="../img/logo1.jpg">
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php