5 Ways to Validate Phone Numbers in PHP

Validating phone numbers is a common requirement for ensuring data quality and reliable user communication in PHP. We will explore five distinct methods for this task, complete with working code, while also examining the pitfalls of traditional approaches and how Abstract API provides a more robust solution.

How to Implement Phone Number Validation in PHP

Here are a few common methods to validate phone numbers in PHP. Each approach offers a different way to check if a phone number format is correct.

Dedicated Regular Expression with preg_match

This approach uses a dedicated regular expression, or regex, to check phone numbers. A well-maintained pattern can enforce the E.164 standard, which formats numbers with a plus sign, country code, and subscriber number. The total length can be up to 15 digits.

The preg_match function in PHP executes the regex search. It returns true if the pattern matches the phone number string and false otherwise. This method gives you full control over the validation pattern and adds zero external dependencies to your project.

function isValidE164(string $n): bool {
    return (bool)preg_match('/^\+?[1-9]\d{1,14}$/', $n);
}

filter_var with FILTER_VALIDATE_REGEXP

You can also use PHP's built-in filter_var function for validation. When paired with the FILTER_VALIDATE_REGEXP flag, it lets you use the same regex pattern while the core extension handles the input filter work.

A key feature of this function is its ability to work with filter_input(). This allows you to connect it directly into input-filter chains for POST, GET, or CLI data without extra wrapper code.

$ok = filter_var(
    $n,
    FILTER_VALIDATE_REGEXP,
    ['options' => ['regexp' => '/^\+?[1-9]\d{1,14}$/']]
);

Google libphonenumber Ports

For more advanced validation, you can use ports of Google's libphonenumber library. Popular PHP versions include giggsey/libphonenumber-for-php and brick/phonenumber, which you can install with Composer. These libraries contain the full metadata set that Google maintains.

This metadata provides several benefits for free.

• Length checks
• Country-specific rules
• Emergency and short-code detection
• Number format
• "Possible vs valid" logic

// Install with Composer: composer require giggsey/libphonenumber-for-php

// With giggsey/libphonenumber-for-php
$util  = \libphonenumber\PhoneNumberUtil::getInstance();
$proto = $util->parse($n, $iso2);          // e.g. “US”
$ok    = $util->isValidNumber($proto);

// Or with Brick
$p  = \Brick\PhoneNumber\PhoneNumber::parse($n, $iso2);
$ok = $p->isValidNumber();

Challenges of Implementing Phone Number Validation

These validation methods present several practical challenges. They struggle with diverse international formats, cannot confirm a number's live status, and rely on data that quickly becomes outdated.

• International number plans constantly evolve. A static regex used with preg_match or filter_var will miss valid cases. Even libphonenumber requires constant metadata updates to remain accurate across different regions and their unique formatting rules.
• A number can pass syntax checks with preg_match or libphonenumber yet be unreachable. These methods only confirm the format. They cannot detect disposable numbers, ported lines, or if the phone is active without external checks.
• Phone number data decays quickly as records turn invalid each month. The metadata libphonenumber caches in your codebase drifts from reality. This forces frequent package updates and production rollouts to maintain fresh data.
• Even mature libraries like libphonenumber fail on edge cases. Issues include confusion over maximum length, local-only numbers, and special territories. These problems force developers to patch rules or add custom logic on top of the library.