How is the parameter passing method of PHP functions reflected in named parameters?

In PHP, named parameters allow specifying parameter names, which can be combined with pass-by-value and pass-by-reference. Passing by value copies the parameter value, and modifications within the function do not affect the original value. The copied parameter address is passed by reference, and the internal modification of the function directly changes the original value.

The parameter passing method of PHP function is reflected in the named parameters

In PHP, there are two ways to pass parameters : Pass by value and pass by reference. When using named parameters, you can explicitly specify the name of the parameter, thereby distinguishing different parameters and handling them differently depending on how they are passed.

Pass by value

When using pass by value, the parameter value passed into the function will be copied to the inside of the function. In this case, any modifications to the parameter value inside the function will not affect the original value.

function example(int $number) {
  $number++; // 修改了函数内部的 $number
}

$num = 10;
example($num); // $num 仍然是 10，因为函数的参数是按值传递的

Pass by reference

When using pass by reference, the parameter address passed into the function will be copied to the inside of the function. This means that modifications to parameter values ​​within the function directly affect the original value.

In order to use pass by reference, you need to add a & symbol before the parameter type.

function example(int &$number) {
  $number++; // 修改了函数内部的 $number，也修改了原始 $num
}

$num = 10;
example($num); // $num 现在是 11，因为函数的参数是按引用传递的

Reflection in named parameters

When using named parameters, you can pass parameters by using the : symbol in the parameter list, then specifying the parameter name and assigning a value. At this time, PHP will automatically match the corresponding value based on the parameter name.

Named parameters combine the advantages of passing by value and passing by reference. When a parameter is passed by value, it automatically creates a copy of the parameter value. However, if you need to modify the original value inside the function, you can pass it by reference by prepending the & symbol to the parameter name.

For example, the following function performs different operations based on the $operation parameter.

function calculator(int $num1, int $num2, string $operation) {
  switch ($operation) {
    case 'add':
      $result = $num1 + $num2;
      break;
    case 'subtract':
      $result = $num1 - $num2;
      break;
    case 'multiply':
      $result = $num1 * $num2;
      break;
    case 'divide':
      if ($num2 !== 0) {
        $result = $num1 / $num2;
      } else {
        throw new DivisionByZeroError;
      }
      break;
  }

  return $result;
}

$num1 = 10;
$num2 = 5;
$operation = 'add'; // 可以使用命名参数显式指定参数名称
$result = calculator(num1: $num1, num2: $num2, operation: $operation);

By using named parameters, you can improve the readability and maintainability of your code and clearly specify the name and delivery method of each parameter. This helps avoid errors when passing parameters and makes the code easier to debug.

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