$re = '~\[2017\/(?:(?!\[\d{4}\/\d{1,2}\/\d)[\s\S])*?ID:00000015fd6c~';
$str = '[2017/4/16 2:28:29AM] (I) Radio mode changed to
SYSAXRADIO_E_STATE_PAGER_RX_SYNC on 170.9 MHz
[2017/4/16 2:28:37AM] Tock = 1718
(I) IDTAG TAG : -90dBm : ID:00000015fd6c
(I) ***************
(I) ID TAG DETECTED 00000015FD6C
(I) ***************';
preg_match_all($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