PHP preg_match() : expressions régulières (Regex)

What is Regular expression in PHP?

PHP regular expressions, also known as regex, are a powerful pattern matching tool that can be performed in a single expression. Regular expressions use special characters such as +, -, and ^ to create complex expressions. They can help you accomplish tasks such as validating email addresses, IP addresses, and more.

Pourquoi utiliser des expressions régulières

• PHP regular expressions simplify identifying patterns in string data by calling a single function. This saves us coding time.
• When validating user input such as email addresses, domain names, telephone numbers, and IP addresses
• Mettre en évidence des mots-clés dans les résultats de recherche
• Lors de la création d'un modèle HTML personnalisé. Regex en PHP peut être utilisé pour identifier les balises de modèle et les remplacer par des données réelles.

Fonctions d'expression régulière intégrées en PHP

PHP has built-in functions that allow us to work with regular expressions, which we will learn in this tutorial. Let us look at the commonly used regular expression functions in PHP.

• preg_match() in PHP – this function is used to perform pattern matching on a string. It returns true if a match is found and false if a match is not found.
• preg_split() in PHP – this function is used to perform a pattern match on a string and then split the results into a numeric array.
• preg_replace() en PHP – cette fonction est utilisée pour effectuer une correspondance de modèle sur une chaîne, puis remplacer la correspondance par le texte spécifié.

Below is the syntax for a regular expression function such as preg_match(), preg_split(), or preg_replace().

<?php
function_name('/pattern/',subject);
?>

ICI,

• “function_name(…)” is either preg_match(), preg_split(), or preg_replace().
• “/…/” the forward slashes denote the beginning and end of our regular expression
• “‘/pattern/'” is the pattern that we need to match
• « sujet » est la chaîne de texte à comparer

Let us now look at practical examples that implement the above PHP regex functions.

Preg_match() en PHP

The first example uses the preg_match() function to perform a simple pattern match for the word guru in a given URL.

The code below shows the implementation of the preg_match() function for the above example.

<?php
$my_url = "www.guru99.com";
if (preg_match("/guru/", $my_url))
{
echo "the url $my_url contains guru";
}
else
{
echo "the url $my_url does not contain guru";
}
?>

Naviguez vers le URL http://localhost/phptuts/preg_match_simple.php

Let us examine the part of the code responsible for our output, preg_match(‘/guru/’, $my_url). HERE,

• "preg_match(…)" est la fonction regex PHP
• « '/guru/' » est le modèle d'expression régulière à faire correspondre
• « $my_url » est la variable contenant le texte à comparer.

PHP Preg_split()

Let us now look at another example that uses the preg_split() function.

Nous allons prendre une phrase de chaîne et la décomposer en un tableau ; le motif à faire correspondre est un espace unique.

La chaîne de texte à utiliser dans cet exemple est « I Love Regular Expressions ».

Le code ci-dessous illustre l'implémentation de l'exemple ci-dessus.

<?php

$my_text = "I Love Regular Expressions";

$my_array = preg_split("/ /", $my_text);

print_r($my_array );

?>

Naviguez vers le URL http://localhost/phptuts/preg_split.php

PHP Preg_replace()

Let us now look at the preg_replace() Fonction PHP qui effectue une correspondance de modèle, puis remplace le modèle par autre chose.

Le code ci-dessous recherche le mot gourou dans un string.

It replaces the word guru with the word guru surrounded by CSS code that highlights the background color.

<?php

$text = "We at Guru99 strive to make quality education affordable to the masses. Guru99.com";

$text = preg_replace("/Guru/", '<span style="background:yellow">Guru</span>', $text);

echo $text;

?>

Assuming you have saved the file preg_replace.php, browse to the URL http://localhost/phptuts/preg_replace.php

Métacaractères d'expression régulière

The above examples used very basic patterns. Metacharacters allow us to perform more complex pattern matches, such as testing the validity of an email address. Let us now look at the commonly used metacharacters.

La liste ci-dessus ne donne que les métacaractères les plus couramment utilisés dans les expressions régulières.

Let us now look at a fairly complex example that checks the validity of an email address.

<?php
$my_email = "name@company.com";
if (preg_match("/^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\.[a-zA-Z.]{2,5}$/", $my_email)) {
echo "$my_email is a valid email address";
}
else
{
echo "$my_email is NOT a valid email address";
}
?>

Explaining the Email Validation Pattern

ICI,

• “/…/” starts and ends the regular expression
• “^[a-zA-Z0-9._-]” matches any lower or upper case letters, numbers between 0 and 9, and dots, underscores, or dashes.
• “+@[a-zA-Z0-9-]” matches the @ symbol followed by lower or upper case letters, numbers between 0 and 9, or dashes.
• “+\.[a-zA-Z.]{2,5}$/” escapes the dot using the backslash, then matches any lower or upper case letters with a character length between 2 and 5 at the end of the string.

Naviguez vers le URL http://localhost/phptuts/preg_match.php

As you can see from the above breakdown, metacharacters are very powerful when it comes to matching patterns.

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