$re = '/[0-9]+\s?(heures?|h)([0-9]+)?/m';
$str = 'I should leave the house at 16h45 but I am late and I should not be arriving between 2 h or 3h or maybe 4heures
2h / 2h / 2 heure / 2heure / 2 heures / 2heures to #hour';
preg_match_all($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