$re = '/(?><STARTTAG1>(?<text1>.*?)<ENDTAG1>)(?:(?!<STARTTAG1>).)*?<STARTTAG2>(?<text2>.*?)<ENDTAG2>/s';
$str = 'Some random text here <STARTTAG1>text to match<ENDTAG1> some more
random text <STARTTAG2>text to match<ENDTAG2> more random text
Some random text here <STARTTAG1>I don\'t want this text to match<ENDTAG1> some more
random text more random text
Some random text here <STARTTAG1>text to match<ENDTAG1> some more
random text <STARTTAG2>text to match<ENDTAG2> more random text ';
preg_match_all($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