$re = '/((([^ ]+) +(me debe) +(\d+) *([^ ]+)? *((del?|por ?e?l?) +(.+))?)|((le debo) +(\d+) *([^ ]+)? *(a ([^ ]+)) *((del?|por ?e?l?) +(.+))?)|((le debo) +(\d+) *([^ ]+)? *((del?|por ?e?l?) +(.+))?(a ([^ ]+))))/';
$str = 'Anota que le debo 3€ a Antonio
Anota que le debo 3€ a Antonio del Monster
Anota que le debo 3€ del Monster a Antonio
Anota que @EsclavoDeLaLuna me debe 6 euros del monster';
preg_match_all($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