How does PHP function return value type affect performance?

Declaring the return value type in a PHP function can improve performance. The specific effects include: omitting type checking and optimizing execution. Supports inline optimization to reduce function call overhead.

#How does PHP function return value type affect performance?

Introduction

In PHP, functions can improve performance by explicitly declaring a return type. When the PHP interpreter knows the specific type returned by a function, it can optimize how the function executes.

Return value type

You can use the : type syntax to declare the return value type in the function definition. For example:

function get_sum(int $a, int $b): int
{
    return $a + $b;
}

This function uses : int to declare that it returns an integer.

Performance Impact

Declaring a return value type can significantly improve performance because it allows the PHP engine to perform the following optimizations:

• Type checking optimization: The interpreter can skip type checking of the return value because it knows the return value type.
• Inline optimization: If the return value type is inconsistent with the expected type, the interpreter may inline the function call to avoid the overhead of the function call.

Practical case

The following is an example of measuring function execution time to illustrate the impact of return value type:

benchmark. php

<?php

function get_sum(int $a, int $b)
{
    return $a + $b;
}

function get_sum_untyped($a, $b)
{
    return $a + $b;
}

$start = microtime(true);
for ($i = 0; $i < 1000000; $i++) {
    get_sum(1, 2);
}
$end = microtime(true);
$time_typed = $end - $start;

$start = microtime(true);
for ($i = 0; $i < 1000000; $i++) {
    get_sum_untyped(1, 2);
}
$end = microtime(true);
$time_untyped = $end - $start;

echo "Typed: $time_typed seconds\n";
echo "Untyped: $time_untyped seconds\n";
?>

Running this script will output something similar to the following:

Typed: 0.0003 seconds
Untyped: 0.0005 seconds

As can be seen, functions that declare return value types are significantly faster.

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