README

This is a wrapper around regular expressions.

Regular expressions in PHP are a common point of failure and working with match groups in particular can be a major headache. Inspired by the functionality Kotlin offers with its Regex class, I decided to start implementing a similar functionality for PHP. Hoping that one day, the PHP team will improve the preg_* functions, this library provides a very simple wrapper around regular expressions in PHP.

In contrast to the Kotlin implementation, the delimiters (e.g. / at the beginning and end of the expression) have to be set. This allows for greater flexibility.

Installation

Requirements

• PHP 8.1+

Composer

composer require hoels/regex

Documentation

Regex class

The main class of this library is the Regex class. The class currently provides the following functions:

containsMatchIn

Regex::containsMatchIn(string $regex, string $input): bool

Indicates whether there is at least one match in $input for the regex given in $regex.

find

Regex::find(string $regex, string $input): MatchResult|null

Returns the first match in $input for the regex given in $regex. Returns null if there is no match and an MatchResult object if there is a match.

findAll

Regex::findAll(string $regex, string $input): MatchResult[]

Returns an array of MatchResult objects for all matches in $input for the regex given in $regex. Returns an empty array if there is no match.

matchAt

Regex::matchAt(string $regex, string $input, int $index): MatchResult|null

Returns the first match in $input for the regex given in $regex, only if the match starts at $index. Returns null if there is no match and an MatchResult object if there is a match at $index.

replace

Regex::replace(string $regex, string $input, string $replacement): string

Replaces all occurrences of $regex in $input by the replacement expression $replacement. Example:

echo Regex::replace("/(\\d\\.\\d)\\.\\d+/", "We support PHP 8.1.26 and 8.2.13.", "$1"); // We support PHP 8.1 and 8.2.

replaceFirst

Regex::replaceFirst(string $regex, string $input, string $replacement): string

Replaces the first occurrence of $regex in $input by the replacement expression $replacement. Example:

echo Regex::replaceFirst("/(\\d\\.\\d)\\.\\d+/", "We support PHP 8.1.26 and 8.2.13.", "$1"); // We support PHP 8.1 and 8.2.3.

MatchResult class

The MatchResult class has three properties:

• value (string): The matched string.
• offset (int): The offset of the matched string within the input string.
• groups (MatchGroup[]): An array of all matched groups.

Groups

The groups property contains an array of MatchGroup objects.

The first element (index 0) will always represent the matched string, therefore the value and offset properties of the MatchGroup object will be the same as the ones of its MatchResult parent.

If the regular expression did not declare any groups, the first element will be the only one in the array.

If the regular expression does declare groups, there will be a MatchGroup object for every group in the order of appearance. Therefore, the first group will have the index 1, the second the index 2, and so on. If there are named groups, there will be additional array elements with the name as index. Note that the MatchGroup object will have the same properties as the one with the numeric index, but the object reference will not be the same.

MatchGroup class

The MatchGroup class has two properties:

• value (string|null): The matched string or null if the declared group is outside the matched string.
• offset (int): The offset of the matched string within the input string. -1 if the declared group is outside the matched string.

Usage

Regex::containsMatchIn

use Regex\Regex;

if (Regex::containsMatchIn(pattern: "/^[a-z]+$/", subject: $_GET["input"])) {
    ...
}

Regex::find

use Regex\Regex;

$matchResult = Regex::find(pattern: "/(?P<year>\d{4})\/(?P<month>\d{2})\/(?P<day>\d{2})/", subject: $input);
if ($matchResult !== null) {
    $year = $matchResult->getGroup("year")?->getValue();
    $month = $matchResult->getGroup("month")?->getValue();
    $day = $matchResult->getGroup("day")?->getValue();
}