Preg_replace for substitution in PHP - Mini Project: Build & Apply

Preg_replace for substitution

📖 Scenario: You are working on a simple text editor tool that needs to replace certain words in a sentence with new words. This is a common task when cleaning or updating text data.

🎯 Goal: Build a PHP script that uses preg_replace to substitute specific words in a given sentence with new words.

📋 What You'll Learn

Create a variable $sentence with the exact text: "The cat sat on the mat."

Create a variable $pattern that matches the word "cat"

Create a variable $replacement with the text "dog"

Use preg_replace with $pattern, $replacement, and $sentence to create a new variable $new_sentence

Print the value of $new_sentence

💡 Why This Matters

🌍 Real World

Text substitution is useful in editing documents, cleaning data, or customizing messages automatically.

💼 Career

Many programming jobs require manipulating text data, and knowing how to use regular expressions with functions like <code>preg_replace</code> is a valuable skill.

1

DATA SETUP: Create the initial sentence

Create a variable called $sentence and set it to the string "The cat sat on the mat." exactly.

PHP

# Create a variable called $sentence with the exact text "The cat sat on the mat."
# Your code here

Need a hint?

Use double quotes to create the string exactly as shown.

2

CONFIGURATION: Define the pattern and replacement

Create a variable called $pattern and set it to the regex pattern that matches the word "cat" exactly. Then create a variable called $replacement and set it to the string "dog".

PHP

<?php
$sentence = "The cat sat on the mat.";
# Create $pattern to match the word "cat"
# Create $replacement with the text "dog"
# Your code here

Need a hint?

Remember to put the pattern between slashes / for regex in PHP.

3

CORE LOGIC: Use preg_replace to substitute the word

Use preg_replace with $pattern, $replacement, and $sentence to create a new variable called $new_sentence.

PHP

<?php
$sentence = "The cat sat on the mat.";
$pattern = "/cat/";
$replacement = "dog";
# Use preg_replace to create $new_sentence
# Your code here

Need a hint?

Use the syntax: preg_replace(pattern, replacement, subject).

4

OUTPUT: Print the new sentence

Write a print statement to display the value of $new_sentence.

PHP

<?php
$sentence = "The cat sat on the mat.";
$pattern = "/cat/";
$replacement = "dog";
$new_sentence = preg_replace($pattern, $replacement, $sentence);
# Print $new_sentence
# Your code here

Need a hint?

Use print($new_sentence); to show the result.