Case conversion functions in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of strtolower and strtoupper

What is the output of this PHP code?

PHP

<?php
$text = "Hello World!";
echo strtolower($text) . " - " . strtoupper($text);
?>

A hello world! - HELLO WORLD!

B HELLO WORLD! - hello world!

C Hello World! - Hello World!

D hello world! - hello world!

💡 Hint

strtolower converts all letters to lowercase, strtoupper converts all letters to uppercase.

The function strtolower converts all characters in the string to lowercase, and strtoupper converts all characters to uppercase. So the output is the lowercase version, then a dash, then the uppercase version.

❓ Predict Output

intermediate

Output of ucfirst and lcfirst

What is the output of this PHP code?

PHP

<?php
$text = "hello WORLD!";
echo ucfirst($text) . " - " . lcfirst(strtoupper($text));
?>

A Hello WORLD! - Hello WORLD!

B hello WORLD! - Hello WORLD!

C Hello WORLD! - hELLO WORLD!

D hello WORLD! - hELLO world!

💡 Hint

ucfirst makes first letter uppercase, lcfirst makes first letter lowercase.

ucfirst makes the first character uppercase and leaves the rest unchanged. strtoupper converts all letters to uppercase, then lcfirst makes the first letter lowercase again.

❓ Predict Output

advanced

Output of mb_convert_case with mixed UTF-8 string

What is the output of this PHP code using mb_convert_case with UTF-8 encoding?

PHP

<?php
$text = "mÜnchEn ist schön";
echo mb_convert_case($text, MB_CASE_TITLE, "UTF-8");
?>

A mÜnchEn ist schön

B München Ist Schön

C MÜNCHEN IST SCHÖN

D MünchEn Ist Schön

💡 Hint

MB_CASE_TITLE capitalizes the first letter of each word correctly for UTF-8 strings.

mb_convert_case with MB_CASE_TITLE converts the first character of each word to uppercase and the rest to lowercase, respecting UTF-8 characters like Ü and ö.

❓ Predict Output

advanced

Output of strcasecmp function

What is the output of this PHP code?

PHP

<?php
$a = "Hello";
$b = "hello";
$result = strcasecmp($a, $b);
echo $result > 0 ? "A" : ($result < 0 ? "B" : "C");
?>

A A

B Error

C B

D C

💡 Hint

strcasecmp compares strings ignoring case and returns 0 if equal.

strcasecmp compares two strings case-insensitively. Since "Hello" and "hello" are equal ignoring case, it returns 0, so the output is "C".

🧠 Conceptual

expert

Why use mb_strtolower over strtolower?

Why should you use mb_strtolower instead of strtolower when working with UTF-8 strings in PHP?

A mb_strtolower correctly converts multibyte UTF-8 characters to lowercase, while strtolower only works reliably with ASCII characters.

B mb_strtolower is faster than strtolower for all strings.

C strtolower converts strings to uppercase, mb_strtolower converts to lowercase.

D mb_strtolower only works with ASCII, strtolower works with UTF-8.

💡 Hint

Think about characters like accented letters or non-English alphabets.

strtolower only handles single-byte ASCII characters correctly. For UTF-8 strings with multibyte characters (like accented letters), mb_strtolower is needed to convert them properly to lowercase.