PHP: How to validate a phone number if well formed?

Question

Using PHP, how can I verify if a phone # is well formed?

It seems easiest to simply strip all non-numeric data, leaving only the numbers. Then to check if 10 digits exist.

Is this the best and easiest way?

Answer 1

You can use a regex for it:

$pattern_phone = "|^[0-9\+][0-9\s+\-]*$|i";
if(!preg_match($pattern_phone,$phone)){
    //Somethings wrong
}

Haven't tested the regex, so it may not be 100% correct.

Answer 2

Checking for 10 digits after stripping will check the syntax but won't check the validity. For that you'd need to determine what valid numbers are available in the region/country and probably write a regex to match the patterns.

Answer 3

What format you need? You can use regular expressions to this.

Answer 4

The best? No. Issues I see with this approach:

• Some area codes - like 000-###-#### - are not valid. See http://en.wikipedia.org/wiki/List_of_NANP_area_codes
• Some exchanges - like ###-555-#### - are not valid. See http://en.wikipedia.org/wiki/555_%28telephone_number%29
• Some people will enter a 1 before their number, i.e. 1-###-###-####.
• Some people are only reachable at an extension, like ###-###-#### x####.
• Some companies tack on extra digits, like 1-800-GO-FLOWERS. The additional digits are simply ignored by the phone system, but a user might expect to be able to enter the whole thing.
• International phone numbers are not necessarily 10 digits, even if you discount the country codes.

Good enough? Quite possibly, but that's up to you and your app.

Answer 5

The problem with validating/filtering data like this usually comes down the the answer to this question: "How strict do I want to be?" which then devolves into a series of "feature" questions

• Are you going to accept international numbers?
• Are you going to accept extensions?
• Are you going to allow various formats i.e., (111) 222-3333 vs 111.222.3333

Depending on your business rules, the answers to these questions can vary. But to be the most flexible, I recommend 3 fields to take a phone number

1. Country Code (optional)
2. Phone Number
3. Extension (optional)

All 3 fields can be programmatically limited/filters for numeric values only. You can then combine them before storing into some parse-able format, or store each value individually.

Answer 6

Answering if something is "the best" thing to do, is nearly impossible (unless you're the one answering your own question).

The way you propose it, stripping all non-digits and then check if there are 10 digits, might result in unwanted behaviour for a string like:

George Washington (February 22, 1732 – December 14, '99) was the commander of the Continental Army in the American Revolutionary War and served as the first President of the United States of America.

since stripping all non-digits will result in the string 2217321499 which is 10 fdigits long, but I highly doubt that the entire string should be considered as a valid phone number.