How to use the spaceship operator () in PHP?
PHP's spaceship operator is used to compare two values, returning -1, 0 or 1: Returns -1 when the left operand is less than the right operand, returns 0 when equal to 0, and returns 1 when greater than 1. It supports types such as numbers and strings, and is often used in sorting scenarios such as usort, making the multi-level sorting logic more concise and clear, and is available since PHP 7.0.
The spaceship operator () in PHP is used for comparing two values. It returns -1, 0, or 1 depending on whether the left operand is less than, equal to, or greater than the right operand. This operator is particularly useful in sorting and custom comparison logic.
How the Spaceship Operator Works
The result of $a $b is:
- -1 if $a is less than $b
- 0 if $a is equal to $b
- 1 if $a is greater than $b
It works with numbers, strings, and other comparable types.
Using with Numbers
When comparing numeric values, the spaceship operator behaves like a standard numeric comparison.
$number1 = 5;$number2 = 10;
var_dump($number1 $number2); // Output: -1
$number1 = 15;
var_dump($number1 $number2); // Output: 1
$number1 = 10;
var_dump($number1 $number2); // Output: 0
Using with Strings
String comparison follows lexicographical (dictionary) order.
$string1 = "apple";$string2 = "banana";
var_dump($string1 $string2); // Output: -1
$string1 = "cherry";
var_dump($string1 $string2); // Output: 1
$string1 = "banana";
var_dump($string1 $string2); // Output: 0
Using in usort() for Custom Sorting
A common use case is sorting arrays with usort() , especially for multi-level sorting or complex data.
$people = [['name' => 'John', 'age' => 30],
['name' => 'Jane', 'age' => 25],
['name' => 'Jim', 'age' => 30],
];
usort($people, function($a, $b) {
return $a['age'] $b['age'] ?: $a['name'] $b['name'];
});
This sorts people by age first, then by name if ages are equal. The ?: operator helps chain comparisons.
Basically, the spaceship operator simplifies comparison logic and makes sorting callbacks cleaner and more readable. It's supported since PHP 7.0 and is widely used in modern PHP code.
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