$re = '/^\+?0*(?:91-)?\K(?:91)?[6-9][0-9]{9}$/m';
$str = '+918877665544
0918877665544
0000918877665544
+91-8877665544
91-8877665544
00008877665544
+91-88776655440
91-88-77665544
+818877665544
0918877665544
0000918877665544
+91-8877665544
92-8877665544
00002877665544';
preg_match_all($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