php 53 lines · 8 steps

Normalizing phone numbers to E.164 in PHP

A static helper cleans arbitrary phone input, applies a country prefix, and validates it against the E.164 format.

Explained by highlit

Intermediate input-validation normalization regular-expressions static-methods

1<?php
2 
3namespace App\Support;
4 
5use InvalidArgumentException;
6 
7final class PhoneNumber
8{
9    private const COUNTRY_PREFIXES = [
10        'US' => '1',
11        'GB' => '44',
12        'FR' => '33',
13        'DE' => '49',
14        'IN' => '91',
15    ];
16 
17    public static function toE164(string $input, string $defaultRegion = 'US'): string
18    {
19        $trimmed = trim($input);
20        $hasPlus = str_starts_with($trimmed, '+');
21        $digits = preg_replace('/\D+/', '', $trimmed);
22 
23        if ($digits === '' || strlen($digits) < 8) {
24            throw new InvalidArgumentException("Phone number '{$input}' has too few digits.");
25        }
26 
27        if (!$hasPlus) {
28            $digits = self::applyDefaultRegion($digits, $defaultRegion);
29        }
30 
31        if (strlen($digits) > 15) {
32            throw new InvalidArgumentException("Phone number '{$input}' exceeds the E.164 maximum length.");
33        }
34 
35        return '+' . $digits;
36    }
37 
38    private static function applyDefaultRegion(string $digits, string $region): string
39    {
40        $prefix = self::COUNTRY_PREFIXES[strtoupper($region)]
41            ?? throw new InvalidArgumentException("Unsupported default region '{$region}'.");
42 
43        if ($region === 'US' && strlen($digits) === 11 && str_starts_with($digits, '1')) {
44            return $digits;
45        }
46 
47        if (str_starts_with($digits, $prefix) && strlen($digits) > 10) {
48            return $digits;
49        }
50 
51        return $prefix . ltrim($digits, '0');
52    }
53}

01 / 01

STEP 01

Walkthrough

Space play ←→ step click any line

Three takeaways

1Strip formatting to raw digits first, then reason about the number as a canonical string.
2Length bounds and a known-prefix lookup catch most malformed input before it propagates.
3Handling the leading-plus case separately lets you infer a region only when the caller didn't specify one.

Related explainers

php

<?php
 
class NameParser
{

Parsing a full name into components in PHP

string-parsing arrays normalization

Intermediate 8 steps

php

<?php
 
namespace App\Services\Checkout;

Validating coupons with Laravel's Pipeline

pipeline chain of responsibility transactions

Intermediate 7 steps

php

<?php
 
namespace App\Services;

How a password strength validator works in PHP

validation regular-expressions data-driven

Intermediate 8 steps

php

<?php
 
namespace App\Services;

Building a cached daily leaderboard in Laravel

caching aggregation eager-loading

Intermediate 9 steps

php

<?php
 
final class RotatingFileLogger
{

How a rotating file logger works in PHP

logging file-rotation io

Intermediate 9 steps

package middleware
 
import (
	"net/http"

Per-plan export limits in Gin middleware

middleware rate-limiting authorization

Intermediate 7 steps

Share this explainer

Here's the card — post it anywhere.

Normalizing phone numbers to E.164 in PHP — share card

Made with highlit — turn any snippet into a walkthrough like this in about a minute.

Explain your code