Case conversion functions in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the PHP function strtolower() do?

It converts all characters in a string to lowercase letters.

beginner

What is the purpose of the PHP function strtoupper()?

It converts all characters in a string to uppercase letters.

beginner

How does ucfirst() function modify a string in PHP?

It converts the first character of the string to uppercase and leaves the rest unchanged.

beginner

What does the PHP function ucwords() do?

It converts the first character of each word in a string to uppercase.

intermediate

Which PHP function would you use to convert a string to lowercase except the first letter of each word?

Use ucwords(strtolower($string)) to first convert the whole string to lowercase, then capitalize the first letter of each word.

Which PHP function converts all letters in a string to uppercase?

A ucfirst()

B strtolower()

C strtoupper()

D ucwords()

strtoupper() changes all characters in a string to uppercase.

What does the ucfirst() function do in PHP?

A Converts the entire string to uppercase

B Converts the entire string to lowercase

C Converts the first character of each word to uppercase

D Converts the first character of the string to uppercase

ucfirst() only changes the first character of the string to uppercase.

If you want to capitalize the first letter of each word in a string, which function should you use?

A strtoupper()

B ucwords()

C strtolower()

D ucfirst()

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

What will strtolower('HELLO World') return?

A 'hello world'

B 'Hello World'

C 'HELLO World'

D 'HELLO world'

strtolower() converts all letters to lowercase.

Which combination of functions converts a string to lowercase and then capitalizes the first letter of each word?

A ucwords(strtolower($string))

B ucfirst(strtolower($string))

C ucwords(strtoupper($string))

D strtoupper(ucwords($string))

First strtolower() makes all letters lowercase, then ucwords() capitalizes the first letter of each word.

Explain how to convert a string to all uppercase and all lowercase in PHP.

Think about functions that change the whole string's letter case.

Describe how to capitalize only the first letter of a string and how to capitalize the first letter of each word in PHP.

One works on the whole string's first letter, the other on each word.

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