All matches with preg_match_all()

PHP course · Advanced · Lesson 43/92

Learn to get all matches in a string with preg_match_all().

All matches with preg_match_all

preg_match finds only the first match. To get every match, use preg_match_all($pattern, $subject, $matches).

The return value is the total match count (0, 1, 2, ...). Matches are stored in $matches using the default PREG_PATTERN_ORDER layout: $matches[0] is an array of all full matches.

So to loop over every hashtag or every number, the foreach ($matches[0] as $m) idiom is common.

PREG_PATTERN_ORDER and PREG_SET_ORDER

The fourth parameter of preg_match_all controls how matches are arranged. Two common options exist:

PREG_PATTERN_ORDER (default): $matches[0] is the list of all full matches, $matches[1] is all matches of the first group. Groups are arranged as columns.

PREG_SET_ORDER: $matches[0] is all groups of the first match, $matches[1] is all groups of the second match. Each match is its own row.

Exercise Find every hashtag

Find every #tag in $post = "Today #php and #regex"; using preg_match_all. Put the pattern into $pattern, call with $matches, and print each tag on a new line with foreach.

Show example solution

Set pattern to "/#\w+/". Call preg_match_all($pattern, $post, $matches). Print with foreach ($matches[0] as $tag) { echo $tag . "\n"; }
Example solution:
<?php
// Find every hashtag (#...) with preg_match_all

$post = "Today #php and #regex";
// Add pattern, matches and the call
$pattern = "/#\w+/";
preg_match_all($pattern, $post, $matches);

// Print each tag on a new line
foreach ($matches[0] as $tag) {
    echo $tag . "\n";
}

Test yourself

What does preg_match_all return?
- The total match count
- The first matched text
- true or false
- The array of matches
Show answer

The total match count — Correct. The return value is the match count; the matches themselves go into $matches.

Loop over the matches

foreach (____ as $tag) {
    echo $tag . "\n";
}

Show answer

foreach ($matches[0] as $tag) {
    echo $tag . "\n";
}

Constants and their meanings

PREG_PATTERN_ORDER

Arranges groups as columns
PREG_SET_ORDER

Arranges matches as rows
$matches[0]

List of all matches
preg_match_all

Function that finds all matches

All matches with preg_match_all()