$re = '~,<([^>]+)>~';
$str = '<https://api.some.com/v1/monitor/zzsomeLongIdzz?access_token=xxSomeLongTokenxx==>; rel="monitor",<https://api.some.com/v1/services/xx/something-more/accounts/2345?access_token=xxSomeLongTokenxx==>; rel="parent"
';
preg_match($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