Character classes and quantifiers in PHP - Mini Project: Build & Apply

Character classes and quantifiers

📖 Scenario: You are working on a simple PHP script to check if certain words match a pattern. This is useful when you want to find words that follow specific rules, like starting with a vowel or having a certain number of letters.

🎯 Goal: Build a PHP script that uses regular expressions with character classes and quantifiers to find words that start with a vowel and have exactly 5 letters.

📋 What You'll Learn

Create a list of words in a PHP array called $words with the exact values: 'apple', 'banana', 'grape', 'orange', 'pear', 'peach'

Create a variable called $pattern that holds a regular expression to match words starting with a vowel (a, e, i, o, u) and having exactly 5 letters

Use a foreach loop with the variable $word to go through each word in $words

Inside the loop, use preg_match with $pattern and $word to check if the word matches the pattern

Print each matching word on its own line using echo

💡 Why This Matters

🌍 Real World

Regular expressions help filter and find text patterns in data, like validating user input or searching documents.

💼 Career

Knowing how to use character classes and quantifiers in regex is useful for web developers, data analysts, and anyone working with text processing.

1

Create the list of words

Create a PHP array called $words with these exact words: 'apple', 'banana', 'grape', 'orange', 'pear', 'peach'

PHP

<?php

// Create the array $words with the given words

Need a hint?

Use square brackets [] to create an array and separate words with commas.

2

Create the regular expression pattern

Create a variable called $pattern that holds the regular expression '/^[aeiou]\w{4}$/' to match words starting with a vowel and having exactly 5 letters

PHP

<?php

$words = ['apple', 'banana', 'grape', 'orange', 'pear', 'peach'];

// Create the regex pattern $pattern

Need a hint?

The pattern starts with ^ for start of word, then a character class [aeiou] for vowels, then \w{4} for exactly 4 word characters, and $ for end of word. Use the i modifier for case-insensitive matching.

3

Check each word with the pattern

Use a foreach loop with variable $word to go through $words. Inside the loop, use preg_match($pattern, $word) to check if the word matches the pattern.

PHP

<?php

$words = ['apple', 'banana', 'grape', 'orange', 'pear', 'peach'];

$pattern = '/^[aeiou]\w{4}$/i';

// Loop through $words and check each word with preg_match

Need a hint?

Use foreach ($words as $word) to loop and preg_match($pattern, $word) to test each word.

4

Print the matching words

Inside the if block, use echo $word . "\n"; to print each matching word on its own line.

PHP

<?php

$words = ['apple', 'banana', 'grape', 'orange', 'pear', 'peach'];

$pattern = '/^[aeiou]\w{4}$/i';

foreach ($words as $word) {
    if (preg_match($pattern, $word)) {
        // Print the matching word
    }
}

Need a hint?

Use echo $word . "\n"; to print each word on a new line.