$re = '/FIRST NAME:([^M]*(?:M(?!ORE DATA:)[^M]*)*)MORE DATA:([^E]*(?:E(?!XTRA DATA:)[^E]*)*)EXTRA DATA:([^F]*(?:F(?!IRST NAME:)[^F]*)*)/';
$str = 'FIRST NAME: sdfksdfkjskdlfjlskdf MORE DATA: dsfkskldfjsdkfjsdkf EXTRA DATA: dsfksdfjlsdjfklsdf FIRST NAME: sdfksdfkjskdlfjlskdf MORE DATA: dsfkskldfjsdkfjsdkf EXTRA DATA: dsfksdfjlsdjfklsdf';
preg_match_all($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