PHP 7 – Combined Comparison (Spaceship) Operator

PHP 7 – Combined Comparison (Spaceship) Operator

In this post we will take a look and another new operator in PHP 7. This operator is the Combined Comparison or Spaceship operator (<=>). This operator is a three way comparison operator. It will do greater-than, less-than and equal comparisons between two operands.

The spaceship operator (<=>) returns -1 if the left side is smaller, 0 if the values are equal and 1 if the left side is larger. It can be used on all generic PHP values with the same semantics as < , <=, ==, >=, >. This operator is similar in behavior to strcmp() or version_compare(). This operator can be used with integers, floats, strings, arrays, objects, etc.

Example usage:

$c = $a <=> $b;
// This is equivalent to
$c = ($a < $b) ? -1 : (($a > $b) ? 1 : 0);

Here are a few more examples from PHP RFP for Combined Comparison (Spaceship) Operator

// Integers
echo 1 <=> 1; // 0
echo 1 <=> 2; // -1
echo 2 <=> 1; // 1
 
// Floats
echo 1.5 <=> 1.5; // 0
echo 1.5 <=> 2.5; // -1
echo 2.5 <=> 1.5; // 1
 
// Strings
echo "a" <=> "a"; // 0
echo "a" <=> "b"; // -1
echo "b" <=> "a"; // 1
 
echo "a" <=> "aa"; // -1
echo "zz" <=> "aa"; // 1
 
// Arrays
echo [] <=> []; // 0
echo [1, 2, 3] <=> [1, 2, 3]; // 0
echo [1, 2, 3] <=> []; // 1
echo [1, 2, 3] <=> [1, 2, 1]; // 1
echo [1, 2, 3] <=> [1, 2, 4]; // -1
 
// Objects
$a = (object) ["a" => "<span class="hiddenGrammarError" pre=""><span class="hiddenGrammarError" pre="">b"]; 
$b</span></span> = (object) ["a" => "b"]; 
echo $a <=> $b; // 0
 
$a = (object) ["a" => "b"]; 
$b = (object) ["a" => "c"]; 
echo $a <=> $b; // -1
 
$a = (object) ["a" => "c"]; 
$b = (object) ["a" => "b"]; 
echo $a <=> $b; // 1
 
// only values are compared
$a = (object) ["a" => "b"]; 
$b = (object) ["b" => "b"]; 
echo $a <=> $b; // 0

More reading:
PHP RFP for Combined Comparison (Spaceship) Operator

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