How to express the two suffix parameters in php

In PHP functions, there are two special parameters: variable number of parameters...$var and callback function callable $callback. A variable number of arguments allows a function to receive any number of arguments, stored as an array. Callback functions allow a function to accept a function and execute it under specific conditions.

Two parameters after the PHP function

In the PHP function, there are two special parameters: ...$var and callable $callback. They allow functions to receive a variable number of arguments and callback functions.

Variable number of parameters:...$var

• Syntax: function functionName(...$var)
• Purpose: Allow the function to accept any number of parameters and store them in the $var variable in the form of an array.
• For example:

function sum(...$numbers) {
  $total = 0;
  foreach ($numbers as $number) {
    $total += $number;
  }
  return $total;
}

echo sum(1, 2, 3, 4, 5); // 输出: 15

Callback function: callable $callback

• Syntax: function functionName(callable $callback )
• Purpose: Allows a function to accept a callback function and execute it under specific conditions.
• For example:

function filterArray(array $array, callable $callback) {
  $filteredArray = [];
  foreach ($array as $element) {
    if ($callback($element)) {
      $filteredArray[] = $element;
    }
  }
  return $filteredArray;
}

$callback = function ($value) {
  return $value > 10;
};

$filteredArray = filterArray([1, 2, 10, 15, 20], $callback); // 输出: [15, 20]

Note:

• The variable number of parameters must be the last parameter in the function parameter list.
• Callback functions can be represented by anonymous functions or function names.

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