$re = '/^(?=.{5}$)[a-z]*\d[a-z]*$/m';
$str = 'jlwk6
bjkgp
5fm8s
x975t
k88q5
zl796
qm9hb
h6gtf
9rm9p
jwzw2';
preg_match_all($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