Preg_match_all for global matching in PHP

Introduction

Preg_match_all helps find all parts of a text that match a pattern, not just the first one.

You want to find every email address in a long text.

You need to get all words that start with a capital letter.

You want to extract all numbers from a sentence.

You want to find all hashtags in a social media post.

Syntax

PHP

int preg_match_all(string $pattern, string $subject, array &$matches, int $flags = PREG_PATTERN_ORDER, int $offset = 0)

$pattern is the pattern you want to find.

$matches will hold all found results after running the function.

Examples

This finds all words starting with 'a' in the text.

PHP

$text = "apple banana cherry";
preg_match_all('/a\w+/', $text, $matches);
print_r($matches);

This finds all groups of digits in the text.

PHP

$text = "123 abc 456 def";
preg_match_all('/\d+/', $text, $matches);
print_r($matches);

Sample Program

This program finds all email addresses in the given text and prints them.

PHP

<?php
$text = "Contact us at [e-mail] or [e-mail].";
preg_match_all('/[\w.-]+@[\w.-]+\.\w+/', $text, $matches);
print_r($matches[0]);
?>

Important Notes

preg_match_all returns the number of matches found.

The matches are stored in $matches as arrays, with full matches in $matches[0].

Summary

Use preg_match_all to find all matches of a pattern in a string.

The results are stored in an array you provide.

This is useful when you want every match, not just the first one.