Spaceship Operator <=> (PHP 7.0)

Also Known As

TL;DR

Explanation

Before PHP 7, writing a comparison callback for usort() required an if/else structure checking equality, greater than, and less than. The spaceship operator <=> compresses this to $a <=> $b. It works on integers, floats, strings, and arrays using PHP's comparison semantics. Multiple sort keys: return $a->priority <=> $b->priority ?: $a->name <=> $b->name. Named for its resemblance to the ASCII art of a spaceship.

Common Misconception

Why It Matters

Common Mistakes

• Forgetting spaceship respects PHP type juggling without strict_types
• Not chaining multiple sort keys with ?: after <=>
• Using manual arithmetic instead of the cleaner <=> operator

Code Examples

// PHP 5 comparison in usort:
usort($items, function($a, $b) {
    if ($a->price === $b->price) return 0;
    return $a->price < $b->price ? -1 : 1;
});

// PHP 7 spaceship operator:
usort($items, fn($a, $b) => $a->price <=> $b->price);

// Multi-key sort:
usort($items, fn($a, $b) =>
    [$a->category, $a->price] <=> [$b->category, $b->price]
);

References

• ↗ https://www.php.net/manual/en/migration70.new-features.php

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