PHP calls method parameters in front of...

In PHP, we can achieve variable number of parameter passing by adding three dots (...) in front of the method parameters. This method is also called "variable parameter list" or "indefinite number of parameters".

Let’s take a look at the specific usage and details.

Basic syntax

In PHP, when we declare a method, we can add three dots in front of the method parameter to indicate that the parameter is variable, for example:

function myFunc(...$args) {
  // 执行代码
}

In this code, the three dots in front of the $args parameter indicate that it is a variable-length parameter list. This means that when calling the myFunc() method, we can pass any number of parameters, and these parameters will be placed in the $args array.

Usage method

When using variable-length parameters, we can call it in the following way:

myFunc(1, 2, 3, 4);

In this example, we call myFunc()# Four parameters are passed in ##, and they will be placed in the $args array.

function extractByKey($key, ...$arrays) {
  $result = array();

  foreach ($arrays as $array) {
    if (array_key_exists($key, $array)) {
      $result[] = $array[$key];
    }
  }

  return $result;
}

$key variable indicating the key name to be extracted. Then we use a variadic argument list to pass the array that needs to be extracted.

$result array to represent the final extracted result. Then we iterate through all the arrays passed in the variable parameters to determine whether $key exists in the array. If it exists, we add the value corresponding to $key in the array to the $result array.

$result array, which contains the specified key-value pairs extracted from all arrays.

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