How is the parameter passing method of PHP function used in variable parameters?

PHP variadic functions allow you to pass any number of arguments, which are passed by value and contained in an array. Use three dots (...) to represent variadic arguments, immediately following the last normal argument. Variadics provide flexibility, allowing you to create general-purpose data processing functions, array merge functions, database functions that handle any number of query parameters, and more.

Parameter passing method of PHP variable parameter function

Variable parameters in PHP function allow the function to accept any number of parameters . Variable parameters are represented by three dots (...) immediately following the last normal parameter.

Parameter passing methods

There are three ways to pass parameters to PHP functions:

• Passing by value: Parameters The value is copied and passed to the function, and any modifications to the parameter value by the function do not affect the original value.
• Pass by reference: The function receives a reference to the original variable, and any modifications to the parameter value by the function will be reflected in the original variable.
• Variadic parameters: Variadic parameters are always passed by value, but it contains an array containing all the provided parameters.

Use of variable parameters

Variable parameters provide great flexibility in functions, allowing you to handle any number of parameters. The following are some practical use cases of variable parameters:

1. General data processing functions

function processData(...$data) {
  // $data 是一个包含所有参数的数组
  foreach ($data as $item) {
    // 对每个参数执行操作
  }
}

processData(1, "Hello", true, []); // 处理所有类型的数据

2. Array connection functions

function arrayConcat(...$arrays) {
  // $arrays 是一个包含所有参数（数组）的数组
  return array_merge(...$arrays);
}

$array1 = [1, 2, 3];
$array2 = ["a", "b", "c"];
$result = arrayConcat($array1, $array2); // [1, 2, 3, "a", "b", "c"]

3. Handle any number of query parameters

function getDatabase($database, ...$parameters) {
  // $parameters 是一个包含所有查询参数的数组
  $sql = "SELECT * FROM $database WHERE ";
  foreach ($parameters as $key => $value) {
    $sql .= "$key = '$value' AND ";
  }
  $sql = rtrim($sql, "AND ");
  return $sql;
}

$sql = getDatabase("users", "name", "John", "age", 30);
// "SELECT * FROM users WHERE name = 'John' AND age = 30"

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