? PHP Regular Expressions Tutorial

? Quick Overview

PHP supports regular expressions (regex), which are patterns used to match character combinations in strings. Regular expressions are powerful tools for searching and manipulating text, validating inputs, and performing complex search and replace operations.

? Key Concepts

preg_match() – Finds the first match of a pattern
preg_match_all() – Finds all matches
preg_replace() – Replaces matching patterns
preg_split() – Splits strings using regex

? Syntax / Theory

PHP regex functions use Perl Compatible Regular Expressions (PCRE). Patterns are enclosed within delimiters like /pattern/ and can include modifiers such as i for case-insensitive matching.

? Code Example

? View Code Example

// Search for a price pattern using preg_match()
<?php
$text = "The price of the item is $20.";
$pattern = "/\$\d+/";

if (preg_match($pattern, $text, $matches)) {
    echo "Found price: " . $matches[0] . "<br>";
} else {
    echo "No price found.<br>";
}
?>

?️ Live Output / Explanation

Output

Found price: $20

The regex /\$\d+/ matches a dollar sign followed by one or more digits.

? Interactive Explanation

Try modifying the pattern to detect emails or phone numbers. Regular expressions allow flexible pattern matching without complex logic.

? Use Cases

Validating emails, phone numbers, and passwords
Extracting specific data from text
Sanitizing and cleaning user input
Search and replace operations

✅ Tips & Best Practices

Use regex testers to validate patterns before coding
Keep patterns readable and simple
Escape special characters properly
Prefer preg_match_all() when multiple matches are needed

? Try It Yourself

Write a regex to validate an email address
Extract all numbers from a string
Use preg_replace() to remove special characters
Split a sentence into words using preg_split()