Spaceship operator in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to compare two numbers using the spaceship operator.

PHP

<?php
$result = 5 [1] 3;
echo $result;
?>

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

A===

B!=

C==

D<=>

Attempts:

3 left

💡 Hint

Common Mistakes

Using == or === instead of the spaceship operator.

Using != which only checks inequality.

The spaceship operator <=> compares two values and returns -1, 0, or 1.

2fill in blank

medium

Complete the code to compare two variables using the spaceship operator.

PHP

<?php
$a = 10;
$b = 20;
$result = $a [1] $b;
echo $result;
?>

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

A==

B<=>

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or < which return boolean, not -1, 0, or 1.

Using == which only checks equality.

The spaceship operator <=> compares $a and $b and returns -1 because 10 is less than 20.

3fill in blank

hard

Fix the error in the code by replacing the incorrect operator with the spaceship operator.

PHP

<?php
$x = 7;
$y = 7;
$result = $x [1] $y;
echo $result;
?>

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

A<=>

B==

C!=

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using == or === which return true or false, not -1, 0, or 1.

Using != which checks inequality.

The spaceship operator <=> returns 0 when both values are equal.

4fill in blank

hard

Fill both blanks to create a dictionary that maps numbers to their comparison result with 10 using the spaceship operator.

PHP

<?php
$numbers = [8, 10, 12];
$results = [
    [1] => [2] <=> 10,
    10 => 10 <=> 10,
    12 => 12 <=> 10
];
print_r($results);
?>

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

A8

B==

C<=>

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of <=> for comparison.

Using != which is not a comparison operator for ordering.

The key is 8 and the value is the result of 8 <=> 10 using the spaceship operator.

5fill in blank

hard

Fill all three blanks to create an array that stores the comparison results of each number with 15 using the spaceship operator.

PHP

<?php
$values = [10, 15, 20];
$comparisons = [
    [1] => [1] <=> 15,
    {{BLANK_3}} => {{BLANK_3}} <=> 15,
    20 => 20 <=> 15
];
print_r($comparisons);
?>

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

A10

B<=>

C15

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of <=> for comparison.

Mixing up keys and values in the array.

The keys are 10 and 15, and the values are the result of comparing each key with 15 using the spaceship operator.

Practice

1. What does the PHP spaceship operator <=> return when comparing two equal values?

easy

A. 1

B. -1

C. 0

D. true

Solution

1. Step 1: Understand the spaceship operator behavior

   The spaceship operator returns -1 if the left value is less, 0 if equal, and 1 if greater.

2. Step 2: Apply to equal values

   When both values are equal, the operator returns 0.

3. Final Answer:

   0 -> Option C

4. Quick Check:

   Equal values return 0 [OK]

Hint: Equal values always return 0 with <=> operator [OK]

Common Mistakes:

• Thinking it returns true or false
• Confusing with comparison operators like == or ===
• Assuming it returns boolean instead of integer

2. Which of the following is the correct syntax to compare two variables $a and $b using the spaceship operator in PHP?

easy

A. $a <=> $b;

B. $a => $b;

C. $a <==> $b;

D. $a <-> $b;

Solution

1. Step 1: Recall the spaceship operator syntax

   The spaceship operator is written as <=> between two values.

2. Step 2: Check each option

   $a <=> $b; uses <=> correctly. Others have invalid or incorrect symbols.

3. Final Answer:

   $a <=> $b; -> Option A

4. Quick Check:

   Correct operator is <=> [OK]

Hint: Spaceship operator is exactly <=> with no extra symbols [OK]

Common Mistakes:

• Using => which is for arrays
• Adding extra equals signs
• Using arrows like <-> which is invalid

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

$x = 5;
$y = 10;
echo $x <=> $y;

medium

A. -1

B. 1

C. 0

D. 10

Solution

1. Step 1: Compare values 5 and 10 using spaceship operator

   Since 5 is less than 10, the operator returns -1.

2. Step 2: Output the result

   The echo statement prints -1.

3. Final Answer:

   -1 -> Option A

4. Quick Check:

   5 < 10 returns -1 [OK]

Hint: Left less than right returns -1 with <=> [OK]

Common Mistakes:

• Confusing output with boolean true or false
• Expecting the right value to print
• Thinking it returns 1 when left is smaller

4. Identify the error in the following PHP code using the spaceship operator:

$a = 7;
$b = 3;
if ($a <=> $b) {
    echo 'a is greater';
}

medium

A. Variables $a and $b are not defined

B. Spaceship operator cannot be used in if condition

C. Missing semicolon after echo statement

D. The condition always evaluates to true except when values are equal

Solution

1. Step 1: Understand spaceship operator in if condition

   The operator returns -1, 0, or 1. In PHP, 0 is false, others are true.

2. Step 2: Analyze the condition with $a=7 and $b=3

   Since 7 > 3, it returns 1, so condition is true and echo runs.

3. Final Answer:

   The condition always evaluates to true except when values are equal -> Option D

4. Quick Check:

   Non-zero spaceship result is true in if [OK]

Hint: Spaceship returns 0 (false) only if values equal [OK]

Common Mistakes:

• Thinking spaceship operator returns boolean
• Expecting it to directly compare like > or <
• Ignoring that 0 is false and others true in if

5. Given an array $numbers = [3, 1, 4, 1, 5], which code snippet correctly sorts it in ascending order using the spaceship operator in a custom comparison function?

hard

A. usort($numbers, fn($a, $b) => $a == $b);

B. usort($numbers, fn($a, $b) => $a <=> $b);

C. sort($numbers, fn($a, $b) => $a <=> $b);

D. usort($numbers, fn($a, $b) => $b <=> $a);

Solution

1. Step 1: Understand sorting with spaceship operator

   To sort ascending, compare $a and $b with $a <=> $b.

2. Step 2: Check correct function usage

   usort accepts a comparison function; sort does not take a callback.

3. Final Answer:

   usort($numbers, fn($a, $b) => $a <=> $b); -> Option B

4. Quick Check:

   Ascending sort uses $a <=> $b with usort [OK]

Hint: Use usort with fn($a,$b) => $a <=> $b for ascending sort [OK]

Common Mistakes:

• Using sort() with a callback function
• Reversing $a and $b for ascending order
• Using equality check instead of comparison