$re = '/<img.*?src=(?:\'|")?data:image\/(?:png|jpeg|jpg|gif);base64,([^\'"\s>]+)/i';
$str = 'Hello, hello, hello <img src="data:image/png;base64,lkqhdklqbhjdkhlqjshdljhqsdhqslkjhdlqhdjlkqshdjlkhsq"> hello hello <img src="data:image/png;base64,ljshqflhsqjlkfhjqsfjlkqhs"> jhfqflsqjk
more stuff. test test test <img src=data:image/png;base64,fhiewgjiewoghiewaghieoaieohigeoaehgieoaheigo alt="test?"> and more.
<img src="http://example.com/image.png"> and more <img alt="test" src=\'data:image/jpg;base64,afejwioagjeoiwajgeiowjgoiewjgoejwgiewjgoewa\' class="img border"> finally.';
preg_match_all($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