$re = '/(style=([\"\']))([^\2]+)(\2)/';
$str = 'style="background-image:url(\'/image/800px/svg_to_png/240726/fossasia2016-2016021130.png\');"';
$subst = "\3";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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