$re = '/^([78]\d{10}|1\d{9}|0\d{6}[78]\d{10}|0\d{7}1\d{9})$/m';
$str = '85556987456
75556987456
1555698745
000000085556987456
000000075556987456
000000001556987456
123091
981279381273
098
asdasd
0123901023910293010293
00000000000000';
preg_match_all($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