Trim functions in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove whitespace from the beginning and end of the string.

PHP

$text = "  Hello World  ";
$trimmed = [1]($text);
echo $trimmed;

Drag options to blanks, or click blank then click option'

Asubstr

Bstrlen

Cstrtoupper

Dtrim

Attempts:

3 left

💡 Hint

Common Mistakes

Using strlen instead of trim.

Using substr which does not remove spaces.

Using strtoupper which changes case but not spaces.

The trim function removes whitespace from both ends of a string.

2fill in blank

medium

Complete the code to remove whitespace only from the beginning of the string.

PHP

$text = "  Hello World  ";
$trimmedStart = [1]($text);
echo $trimmedStart;

Drag options to blanks, or click blank then click option'

Atrim

Bltrim

Crtrim

Dstr_replace

Attempts:

3 left

💡 Hint

Common Mistakes

Using trim which removes spaces from both ends.

Using rtrim which removes spaces from the right end.

Using str_replace which replaces characters but does not trim.

The ltrim function removes whitespace from the start (left side) of a string.

3fill in blank

hard

Fix the error in the code to remove whitespace only from the end of the string.

PHP

$text = "  Hello World  ";
$trimmedEnd = [1]($text);
echo $trimmedEnd;

Drag options to blanks, or click blank then click option'

Atrim

Bltrim

Crtrim

Dsubstr

Attempts:

3 left

💡 Hint

Common Mistakes

Using ltrim which removes spaces from the left.

Using trim which removes spaces from both ends.

Using substr which does not remove spaces.

The rtrim function removes whitespace from the end (right side) of a string.

4fill in blank

hard

Fill both blanks to create an array of trimmed words from the list, removing spaces from both ends.

PHP

$words = ["  apple  ", " banana", "cherry  "];
$trimmedWords = array_map([1], $words);
print_r($trimmedWords);

Drag options to blanks, or click blank then click option'

Atrim

Bltrim

Crtrim

Dstrtoupper

Attempts:

3 left

💡 Hint

Common Mistakes

Using ltrim or rtrim which only remove spaces from one side.

Using strtoupper which changes case but not spaces.

Using trim inside array_map removes spaces from both ends of each word.

5fill in blank

hard

Fill all three blanks to trim spaces from both ends and check if the trimmed string is empty.

PHP

$text = "  ";
$trimmed = [1]($text);
if ($trimmed [2] '' ) {
    echo [3];
} else {
    echo 'Not empty';
}

Drag options to blanks, or click blank then click option'

Atrim

B==

C'Empty string'

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using != instead of == in the condition.

Not trimming before comparison.

Printing wrong message.

First, trim removes spaces. Then, == compares to empty string. If true, print 'Empty string'.

Practice

1. What does the PHP function trim() do to a string?

easy

A. Removes all spaces inside the string

B. Removes whitespace from both the beginning and end of the string

C. Removes only the first character of the string

D. Converts the string to uppercase

Solution

1. Step 1: Understand the purpose of trim()

   The trim() function removes unwanted whitespace characters from the start and end of a string.

2. Step 2: Compare options with function behavior

   Only Removes whitespace from both the beginning and end of the string correctly describes removing whitespace from both ends, not inside or changing case.

3. Final Answer:

   Removes whitespace from both the beginning and end of the string -> Option B

4. Quick Check:

   trim() removes spaces at both ends [OK]

Hint: trim() cleans spaces only at string ends, not inside [OK]

Common Mistakes:

• Thinking trim() removes spaces inside the string
• Confusing trim() with strtoupper()
• Assuming trim() removes only from one side

2. Which of the following is the correct syntax to remove spaces only from the left side of a string in PHP?

easy

A. ltrim($str)

B. rtrim($str)

C. trim($str)

D. strip($str)

Solution

1. Step 1: Identify function for left-side trimming

   The function ltrim() removes whitespace from the left (start) side of a string.

2. Step 2: Check other options

   rtrim() removes from right side, trim() removes both sides, and strip() is not a valid PHP function.

3. Final Answer:

   ltrim($str) -> Option A

4. Quick Check:

   ltrim() trims left side only [OK]

Hint: ltrim() trims left side; rtrim() trims right side [OK]

Common Mistakes:

• Using rtrim() to trim left side
• Using trim() when only left side is needed
• Using non-existent function strip()

3. What will be the output of the following PHP code?

$text = "  Hello World!  ";
echo strlen(trim($text));

medium

A. 15

B. 17

C. 13

D. 11

Solution

1. Step 1: Understand the string and trim effect

   The original string has 2 spaces before and 2 spaces after "Hello World!". The length with spaces is 17.

2. Step 2: Apply trim() and calculate length

   trim() removes spaces at both ends, so the string becomes "Hello World!" which has 12 characters plus 1 for the exclamation mark, total 12 + 1 = 12? Actually, "Hello World!" is 12 characters? Let's count: H(1) e(2) l(3) l(4) o(5) space(6) W(7) o(8) r(9) l(10) d(11) !(12). So 12 characters total. But the option says 13. The original string is " Hello World! " with 2 spaces before and 2 after, total length 17. After trim, spaces removed, length is 12. So 13 is 13, which is incorrect. The correct length is 12. So the correct answer should be 12, but no option has 12. Options are 15, 17, 13, 11. 13 is closest but incorrect. So the code outputs 12, but no option matches. So the question has a bug. We must fix options or correct_answer. Let's check the code: echo strlen(trim($text)); The trimmed string is "Hello World!" length 12. So correct_answer should be none of these. So fix options: change 13 to 12 and correct_answer to C. Or change correct_answer to none. Let's fix 13 to "12" and correct_answer to ["C"].

3. Final Answer:

   12 -> Option C

4. Quick Check:

   trimmed string length = 12 [OK]

Hint: Count characters after removing spaces at ends with trim() [OK]

Common Mistakes:

• Counting spaces inside the string
• Forgetting trim() removes spaces at both ends
• Confusing strlen() output with original string length

4. Identify the error in the following PHP code that tries to remove trailing spaces:

$str = "Test string   ";
$newStr = ltrim($str);
echo "'$newStr'";

medium

A. ltrim() removes spaces from the left, not the right

B. Missing semicolon after echo statement

C. Using single quotes inside echo causes error

D. Variable $newStr is not defined

Solution

1. Step 1: Understand what ltrim() does

   ltrim() removes spaces from the left side of the string, but the spaces are on the right side.

2. Step 2: Check code for other errors

   Semicolons are correct, single quotes inside echo are valid, and $newStr is defined properly.

3. Final Answer:

   ltrim() removes spaces from the left, not the right -> Option A

4. Quick Check:

   Use rtrim() to remove right side spaces [OK]

Hint: Use rtrim() for right side spaces, ltrim() for left [OK]

Common Mistakes:

• Using ltrim() to remove right side spaces
• Thinking single quotes cause errors in echo
• Assuming variable is undefined without reason

5. You have a string $data = "\t Example Text \t" with tabs, newlines, and spaces around it. Which PHP function call will remove all these whitespace characters from both ends?

hard

A. trim($data, " \t\n")

B. ltrim($data, " \t")

C. rtrim($data)

D. trim($data)

Solution

1. Step 1: Understand default trim() behavior

   By default, trim() removes spaces, tabs, newlines, carriage returns, and some other whitespace characters from both ends.

2. Step 2: Check the character mask in options

   trim($data, " \t\n") explicitly specifies space, tab, and newline characters to remove, but the default trim() already removes these and more, so trim($data) is sufficient and preferred.

3. Step 3: Analyze other options

   rtrim() and ltrim() remove only one side, so they won't clean both ends.

4. Final Answer:

   trim($data) -> Option D

5. Quick Check:

   Use trim() to remove all whitespace from both ends [OK]

Hint: Use trim() to remove all whitespace including tabs and newlines [OK]

Common Mistakes:

• Using ltrim() or rtrim() when both ends need trimming
• Assuming trim() removes only spaces, not tabs/newlines
• Not specifying characters when needed for custom trimming