Case conversion functions in PHP - Mini Project: Build & Apply

Case conversion functions

📖 Scenario: You are working on a simple text processing tool that changes the case of words. This is useful when you want to standardize names or titles in a list.

🎯 Goal: Build a PHP script that converts a list of words to uppercase, lowercase, and capitalized forms using PHP's case conversion functions.

📋 What You'll Learn

Create an array of words with exact values

Create a variable to hold the number of words

Use a for loop to convert each word to uppercase and store in a new array

Print the original array and the uppercase array

💡 Why This Matters

🌍 Real World

Changing the case of text is common in data cleaning, formatting user input, or preparing text for display.

💼 Career

Many programming jobs require manipulating strings and arrays, especially for web development and data processing.

1

Create the initial array of words

Create an array called words with these exact values: 'apple', 'Banana', 'Cherry', 'date', 'Elderberry'.

PHP

# Create the array called words with the given values
# Your code here

Hint

Use $words = [ ... ]; to create the array with the exact words.

2

Create a variable for the number of words

Create a variable called count and set it to the number of elements in the $words array using the count() function.

PHP

<?php
$words = ['apple', 'Banana', 'Cherry', 'date', 'Elderberry'];
# Create the variable count with the number of words
# Your code here

Hint

Use count($words) to get the number of words.

3

Convert words to uppercase using a for loop

Create an empty array called upperWords. Use a for loop with the variable i from 0 to $count - 1. Inside the loop, convert $words[i] to uppercase using strtoupper() and store it in upperWords[i].

PHP

<?php
$words = ['apple', 'Banana', 'Cherry', 'date', 'Elderberry'];
$count = count($words);
# Create upperWords array and fill it with uppercase words using a for loop
# Your code here

Hint

Use strtoupper() to convert each word to uppercase inside the loop.

4

Print the original and uppercase arrays

Use print_r() to print the $words array with the label "Original words:". Then print the $upperWords array with the label "Uppercase words:".

PHP

<?php
$words = ['apple', 'Banana', 'Cherry', 'date', 'Elderberry'];
$count = count($words);
$upperWords = [];
for ($i = 0; $i < $count; $i++) {
    $upperWords[$i] = strtoupper($words[$i]);
}
# Print the original and uppercase arrays
# Your code here

Hint

Use print_r() to display arrays with labels.

Practice

1. Which PHP function converts all letters in a string to uppercase?
$text = "hello world";

easy

A. strtoupper()

B. strtolower()

C. ucfirst()

D. ucwords()

Solution

1. Step 1: Understand the function purpose

   strtoupper() converts all characters in a string to uppercase letters.

2. Step 2: Compare with other functions

   strtolower() makes all letters lowercase, ucfirst() capitalizes only the first letter, and ucwords() capitalizes the first letter of each word.

3. Final Answer:

   strtoupper() -> Option A

4. Quick Check:

   Uppercase function = strtoupper() [OK]

Hint: All uppercase letters? Use strtoupper() [OK]

Common Mistakes:

• Confusing strtoupper() with strtolower()
• Using ucfirst() to uppercase whole string
• Using ucwords() for full uppercase

2. Which of the following is the correct syntax to convert a string to lowercase in PHP?
$str = "HELLO";

easy

A. strtolower->$str();

B. strtolower $str;

C. strtolower($str);

D. strtolower{$str};

Solution

1. Step 1: Identify correct function call syntax

   In PHP, functions are called with parentheses enclosing arguments, like functionName(argument);.

2. Step 2: Check each option

   strtolower($str); uses correct syntax: strtolower($str);. Others have syntax errors or invalid usage.

3. Final Answer:

   strtolower($str); -> Option C

4. Quick Check:

   Function call syntax = strtolower($str); [OK]

Hint: Function calls need parentheses around arguments [OK]

Common Mistakes:

• Missing parentheses in function call
• Using arrow or braces incorrectly
• Confusing function call with variable access

3. What is the output of the following PHP code?

$name = "john doe";
echo ucfirst($name);

medium

A. John doe

B. john Doe

C. JOHN DOE

D. john doe

Solution

1. Step 1: Understand ucfirst() behavior

   ucfirst() capitalizes only the first character of the entire string, leaving the rest unchanged.

2. Step 2: Apply to given string

   Input is "john doe". After ucfirst(), it becomes "John doe" (only first letter capitalized).

3. Final Answer:

   John doe -> Option A

4. Quick Check:

   ucfirst("john doe") = "John doe" [OK]

Hint: ucfirst() capitalizes only first letter of whole string [OK]

Common Mistakes:

• Expecting all words capitalized
• Confusing ucfirst() with ucwords()
• Assuming it converts whole string to uppercase

4. The following PHP code is intended to capitalize the first letter of each word in a string, but it does not work as expected:

$text = "hello world";
echo ucfirst($text);

What is the correct fix?

medium

A. Replace ucfirst() with strtoupper()

B. Replace ucfirst() with ucwords()

C. Replace ucfirst() with strtolower()

D. No fix needed, code is correct

Solution

1. Step 1: Identify function behavior

   ucfirst() capitalizes only the first letter of the entire string, not each word.

2. Step 2: Choose function to capitalize each word

   ucwords() capitalizes the first letter of every word in the string.

3. Final Answer:

   Replace ucfirst() with ucwords() -> Option B

4. Quick Check:

   Capitalize each word = ucwords() [OK]

Hint: Use ucwords() to capitalize first letter of each word [OK]

Common Mistakes:

• Using ucfirst() instead of ucwords()
• Using strtoupper() which uppercases all letters
• Thinking code is already correct

5. You have a string with mixed case: $input = "hElLo WoRLd";. You want to convert it so that only the first letter of each word is uppercase and the rest are lowercase. Which PHP code achieves this?

hard

A. $output = ucfirst(strtolower($input));

B. $output = strtoupper(ucwords($input));

C. $output = strtolower(ucfirst($input));

D. $output = ucwords(strtolower($input));

Solution

1. Step 1: Normalize string to lowercase

   Use strtolower() to convert all letters to lowercase first, so mixed case is fixed.

2. Step 2: Capitalize first letter of each word

   Apply ucwords() to capitalize the first letter of every word in the now lowercase string.

3. Final Answer:

   $output = ucwords(strtolower($input)); -> Option D

4. Quick Check:

   Lowercase then ucwords() = desired format [OK]

Hint: Lowercase first, then ucwords() for title case [OK]

Common Mistakes:

• Applying ucwords() before strtolower()
• Using strtoupper() which uppercases all letters
• Using ucfirst() which only capitalizes first letter of string