$re = '/-----BEGIN PUBLIC KEY-----(.*)-----END PUBLIC KEY-----/s';
$str = 'KEY_ID: 1
STATUS: VALID
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEaq6djyzkpHdX7kt8DsSt6IuSoXjp
WVlLfnZPoLaGKc/2BSfYQuFIO2hfgueQINJN3ZdujYXfUJ7Who+XkcJqHQ==
-----END PUBLIC KEY-----';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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