Return value processing mechanism of PHP functions

The return value processing mechanism of the PHP function includes: direct return, use of references, modification of variables outside the function, use of global variables, modification of global variables, use of output parameters to return multiple values ​​

PHP function Return value processing mechanism

Function in PHP can return a value, which can be used by the caller. There are several processing mechanisms for function return values:

1. Direct return

The simplest way is to directly return a value, you can usereturn Statement:

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

$result = sum(5, 10); // $result 将等于 15

2. Use reference

By passing reference parameters, you can modify variables outside the function:

function increment(int &$n) {
  $n++;
}

$n = 5;
increment($n); // $n 将变为 6

3 . Use global variables

You can modify global variables within a function, but this is not recommended because it will destroy the encapsulation of the function:

function add_to_global($x) {
  global $global_var;
  $global_var += $x;
}

$global_var = 5;
add_to_global(10); // $global_var 将变为 15

4. Use output Parameters

The output parameter is a special reference parameter that allows the function to return multiple values ​​​​through its parameters:

function sum_and_product(int $a, int $b, int &$sum, int &$product) {
  $sum = $a + $b;
  $product = $a * $b;
}

$sum = 0;
$product = 0;
sum_and_product(5, 10, $sum, $product); // $sum 将变为 15，$product 将变为 50

Practical case:

In the following example, the calculate_area() function returns the area and perimeter of the rectangle through the output parameters:

function calculate_area(int $length, int $width, int &$area, int &$perimeter) {
  $area = $length * $width;
  $perimeter = 2 * ($length + $width);
}

$length = 5;
$width = 10;
$area = 0;
$perimeter = 0;
calculate_area($length, $width, $area, $perimeter);

echo "面积：$area";
echo "周长：$perimeter";

Output:

面积：50
周长：30

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