$re = '/(\d+)\.\s+\[[^]]+\]\s*`([^`]*)`\s*/';
$str = 'MATCH 1
1. [4-17] `public direct`
2. [18-29] `routing.key`
MATCH 2
1. [35-41] `direct`
2. [42-52] `routingkey` ';
preg_match_all($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