How to use preg_match in phone numbers - PHP : Hello everyone? I'm not a very regular programmer and I need your help. I would like to add a phone number in a registration form, users will need to input username, email, phone number and password. All these fields will be REQUIRED including the phone number. I'm based in Kenya so I would like to limit the Phone number to 13 characters including the + (sign). The No. should like: 
+25470164XXXX OR 070164XXXX both formats are accepted. Kindly assist me on how to implement this using preg_match function in PHP.
Thanks