$re = '/^(?:(?:[,"\n]|"[^"]*"),){2}\K".*?",?(,".*?",)/m';
$str = '"Test","test","test1234","",""
"Test","test","test1234","url_test.com/test",""
"Test","test","test1234","","testing"
"Test","test","test12"34","",""
"Test","test","te\\"st1234","",""
"Test","test","test1"2,34","",""';
preg_match_all($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