Spaceship operator in PHP - Mini Project: Build & Apply

Spaceship Operator in PHP

📖 Scenario: You are building a simple ranking system for a game. You want to compare players' scores to see who is ahead, behind, or tied.

🎯 Goal: Learn how to use the PHP spaceship operator to compare two numbers and understand its output.

📋 What You'll Learn

Create two variables with exact scores

Create a variable to hold the comparison result using the spaceship operator

Print the comparison result

💡 Why This Matters

🌍 Real World

Comparing scores or values quickly is common in games, sorting, and decision-making.

💼 Career

Understanding comparison operators helps in writing clean and efficient code for sorting and conditional logic.

1

Create two score variables

Create two variables called $score1 and $score2 with values 85 and 90 respectively.

PHP

$score1 = 0;
$score2 = 0;
# Create two variables called $score1 and $score2 with values 85 and 90 respectively

Hint

Use the assignment operator = to set the values.

2

Create a comparison variable

Create a variable called $comparison that uses the spaceship operator <=> to compare $score1 and $score2.

PHP

<?php
$score1 = 85;
$score2 = 90;
# Create a variable $comparison that compares $score1 and $score2 using the spaceship operator

Hint

The spaceship operator returns -1, 0, or 1 depending on the comparison.

3

Add a condition to explain the result

Use an if statement to print 'Score1 is less' if $comparison is -1, 'Scores are equal' if 0, and 'Score1 is greater' if 1.

PHP

 $score2;
# Use if statements to print the comparison result as text

Hint

Use strict comparison === to check the value of $comparison.

4

Print the final comparison result

Run the program to print the correct comparison message based on the spaceship operator result.

PHP

 $score2;
if ($comparison === -1) {
    echo 'Score1 is less';
} elseif ($comparison === 0) {
    echo 'Scores are equal';
} else {
    echo 'Score1 is greater';
}
# Run the program to see the output

Hint

The output should tell you which score is smaller or if they are equal.

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