$re = '/(\S+?)=["\']?((?:.(?!["\']?\s+(?:\S+)=|[>"\']))+.)["\']?/';
$str = ' style="width: 462px;" src="data:image/png;base64,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" data-filename="Screenshot from 2016-02-09 21:54:47.png"
';
preg_match_all($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