Trim functions in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of trim() with default characters

What is the output of the following PHP code?

PHP

<?php
$str = "  Hello World!  \n";
echo trim($str);
?>

A " Hello World!"

B " Hello World! \n"

C "Hello World! \n"

D "Hello World!"

💡 Hint

trim() removes whitespace from the start and end of a string.

The trim() function removes spaces, tabs, newlines from both ends of the string. So the output is "Hello World!" without spaces or newline around it.

❓ Predict Output

intermediate

Using trim() with custom character mask

What will this PHP code output?

PHP

<?php
$str = "xxxyHello World!yyx";
echo trim($str, "xy");
?>

A "Hello World!"

B "xyHello World!yyx"

C "Hello World!yyx"

D "xxxyHello World!"

💡 Hint

trim() removes all characters in the mask from both ends.

The mask "xy" means trim removes all 'x' and 'y' characters from start and end. So "xxxy" and "yyx" are removed, leaving "Hello World!".

❓ Predict Output

advanced

Difference between trim(), ltrim(), and rtrim()

What is the output of this PHP code?

PHP

<?php
$str = "  Hello World!  ";
echo '[' . ltrim($str) . ']';
echo '[' . rtrim($str) . ']';
echo '[' . trim($str) . ']';
?>

A [ Hello World! ][ Hello World! ][ Hello World! ]

B [ Hello World!][Hello World! ][Hello World!]

C [Hello World! ][ Hello World!][Hello World!]

D [Hello World!][Hello World!][Hello World!]

💡 Hint

ltrim() removes from left, rtrim() from right, trim() from both ends.

ltrim() removes spaces on the left only, so right spaces remain. rtrim() removes spaces on the right only, so left spaces remain. trim() removes spaces on both ends.

❓ Predict Output

advanced

Behavior of trim() with empty string mask

What will this PHP code output?

PHP

<?php
$str = "  Hello World!  ";
echo trim($str, "");
?>

A " Hello World! "

B "Hello World!"

C SyntaxError

D "Hello World! "

💡 Hint

An empty mask means no characters are removed.

When the character mask is an empty string, trim() does not remove any characters, so the original string is returned unchanged.

🧠 Conceptual

expert

Why does trim() remove characters in any order from the mask?

Consider trim($str, "abc") in PHP. Which statement best explains how characters are removed?

A trim() removes characters only if they appear in the exact order 'abc' at the string ends.

B trim() removes any combination of 'a', 'b', or 'c' characters from the start and end, in any order, until a character not in the mask is found.

C trim() removes only the first character if it matches 'a', then stops.

D trim() removes characters only from the middle of the string if they match 'a', 'b', or 'c'.

💡 Hint

Think about how trim() scans from both ends.

trim() treats the mask as a set of characters. It removes any characters from the start and end that are in the mask, regardless of order, until it finds a character not in the mask.