Spaceship operator in PHP - Step-by-Step Execution

Concept Flow - Spaceship operator

Evaluate left expression

↓

Evaluate right expression

↓

Compare left and right

↓

Return -1 if left < right

↓

Return 0 if left == right

↓

Return 1 if left > right

↓

End

The spaceship operator compares two values and returns -1, 0, or 1 depending on whether the left value is less than, equal to, or greater than the right value.

Execution Sample

PHP

<?php
$result = 5 <=> 3;
echo $result;
?>

This code compares 5 and 3 using the spaceship operator and prints the result.

Execution Table

Step	Left Expression	Right Expression	Comparison	Result
1	5	3	5 > 3	1
2	2	2	2 == 2	0
3	1	4	1 < 4	-1
4	-	-	-	End of comparisons

💡 All comparisons done, operator returns -1, 0, or 1 based on comparison

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
result	undefined	1	0	-1	varies per comparison

Key Moments - 3 Insights

Why does the spaceship operator return 1 when left is greater than right?

Because the operator is designed to return 1 when the left value is greater, as shown in execution_table row 1 where 5 > 3 returns 1.

What happens if both values are equal?

The operator returns 0, indicating equality, as shown in execution_table row 2 where 2 == 2 returns 0.

Can the spaceship operator be used with strings?

Yes, it compares strings lexicographically, returning -1, 0, or 1 just like with numbers.

Visual Quiz - 3 Questions

Look at the execution table, what is the result when left is 1 and right is 4?

A -1

B 1

C 0

D Undefined

💡 Hint

Check execution_table row 3 where left=1 and right=4

At which step does the spaceship operator return 0?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at execution_table row 2 where left and right are equal

If the left expression is less than the right, what does the spaceship operator return?

A 0

B -1

C 1

D It throws an error

💡 Hint

See execution_table row 3 for left < right case

Concept Snapshot

Spaceship operator (<=>) compares two values.
Returns -1 if left < right.
Returns 0 if left == right.
Returns 1 if left > right.
Useful for sorting and comparisons.
Works with numbers and strings.

Full Transcript

The spaceship operator in PHP compares two values and returns -1, 0, or 1 depending on whether the left value is less than, equal to, or greater than the right value. For example, 5 <=> 3 returns 1 because 5 is greater than 3. When both values are equal, like 2 <=> 2, it returns 0. If the left value is less, like 1 <=> 4, it returns -1. This operator is useful for sorting and comparing values easily.