PHP's preg_replace function is a powerful tool for performing regular expression-based search and replace operations on strings. It is widely used in web development for tasks such as input validation, data formatting, and text manipulation. Understanding how to use preg_replace effectively can significantly streamline your PHP development process.

In a Linux environment, PHP scripts can be executed from the command line or as part of a web server setup, such as Apache or Nginx. This article will guide you through using preg_replace in both contexts, providing practical examples to illustrate its usage.

Examples:

1. Basic Usage of preg_replace in a PHP Script

Create a PHP script named example.php with the following content:

<?php
// Sample text
$text = "The quick brown fox jumps over the lazy dog.";

// Regular expression to replace all occurrences of 'fox' with 'cat'
$pattern = "/fox/";
$replacement = "cat";

// Perform the replacement
$result = preg_replace($pattern, $replacement, $text);

echo $result;
?>

To run this script from the command line in a Linux environment, use the following command:

php example.php

This will output:

The quick brown cat jumps over the lazy dog.

2. Using preg_replace with Capture Groups

Capture groups allow you to reference parts of the matched string in the replacement text. Here’s an example:

<?php
// Sample text
$text = "John Doe, Jane Doe";

// Regular expression to swap first and last names
$pattern = "/(\w+) (\w+)/";
$replacement = "$2 $1";

// Perform the replacement
$result = preg_replace($pattern, $replacement, $text);

echo $result;
?>

Running this script will output:

Doe John, Doe Jane

3. Executing PHP Scripts with preg_replace via a Web Server

If you are running a web server like Apache or Nginx, place the PHP script in the web root directory (e.g., /var/www/html for Apache). Create a file named web_example.php with the following content:

<?php
// Sample text
$text = "Hello World!";

// Regular expression to replace 'World' with 'PHP'
$pattern = "/World/";
$replacement = "PHP";

// Perform the replacement
$result = preg_replace($pattern, $replacement, $text);

echo $result;
?>

Access this script via a web browser at http://your_server_ip/web_example.php, and it will display:

Hello PHP!