$re = '/(?:[a-zA-Z\/-]*[0-9]+)+[0-9a-zA-Z\/-]*/m';
$str = ' { em , 680/3 }
no 659-11
no funciona la 2507
a-4-2 no funciona
p-8 con presencia de arena
no 2-5c12s si sirve
mecanica no 1ty -22s brinca';
preg_match_all($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