What are the parameters passing methods for PHP functions? Its type?

Parameter passing method of PHP function: value passing: modification within the function has no effect on the original value. Pass by reference: Modifications within a function will affect the original value. Type hints can specify the transfer method, such as passing by value: function myFunction(int $value), passing by reference: function myFunction(int &$value).

PHP function parameter passing method

In PHP, function parameters can be passed by value or by reference.

Value passing

In value passing, the value of the parameter is copied inside the function. Any modifications to the parameters inside the function will not affect the original values ​​outside the function.

Syntax:

function myFunction(int $value) {
  $value++;
}

Example:

$a = 10;
myFunction($a);
echo $a; // 输出 10，因为参数值被复制了

Pass by reference

In pass by reference, the parameters of the function are not copied. Instead, a reference to the original value is passed. Modifications to the parameters inside the function will affect the original values ​​outside the function.

Syntax:

function myFunction(int &$value) {
  $value++;
}

Example:

$a = 10;
myFunction($a);
echo $a; // 输出 11，因为参数是引用原值

Type hints

The parameter passing method in PHP can also be specified through type hints:

• Pass by value: function myFunction(int $value)
• ##Pass by reference: function myFunction(int &$value)

Type hints can improve the readability and maintainability of your code, but they are not required.

Practical case

Consider a function that calculates pi:

function calculatePi(int $n) {
  $sum = 0;
  for ($i = 1; $i <= $n; $i++) {
    $sum += 1 / (4 * pow(-1, $i) * (2 * $i - 1));
  }
  return $sum;
}

To avoid creating a copy of the $sum array every time the function is called, we can use pass by reference:

function calculatePi(int &$sum, int $n) {
  for ($i = 1; $i <= $n; $i++) {
    $sum += 1 / (4 * pow(-1, $i) * (2 * $i - 1));
  }
}

Now, when we call the function:

$sum = 0;
calculatePi($sum, 10000);
echo $sum; // 输出近似值 π

Using pass by reference can improve the performance of the function, especially when the parameters are large data structures.

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