$re = '/(?<=<(BLK_TYPE)>)(.*?)(?=<\/BLK_TYPE>)/m';
$str = '<?xml version="1.0" encoding="windows-1251" ?><ELEM_LIST><ELEM PLAYER_NAME="Плеер" STATUS="playing"><START_TIME>15:49:41</START_TIME><BLK_TYPE>М</BLK_TYPE><TYPE>М</TYPE><NAME>Heathens</NAME><ARTIST>Twenty One Pilots</ARTIST><AUTHOR></AUTHOR><ALBUM></ALBUM><DBID></DBID><FILE_NAME>H:\\Radio\\Music\\Twenty One Pilots - Heathens.mp3</FILE_NAME><DURATION>00:03:10</DURATION></ELEM><ELEM PLAYER_NAME="Плеер" STATUS="preloaded"><START_TIME></START_TIME><BLK_TYPE>М</BLK_TYPE><TYPE>Д</TYPE><NAME>ID #5</NAME><ARTIST>Jingle</ARTIST><AUTHOR></AUTHOR><ALBUM></ALBUM><DBID></DBID><FILE_NAME>H:\\Radio\\Jingle\'s\\ID #5.mp3</FILE_NAME><DURATION>00:00:01</DURATION></ELEM><ELEM PLAYER_NAME="Плеер" STATUS="preloaded"><START_TIME></START_TI';
preg_match_all($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