PHP closure function Detailed _php tips

Anonymous functions are also called closure functions (closures allows you to create a function that has not been specified, most often as a value for a callback function parameter.)

The closure function does not have a function name, and the defined variable is treated as a function directly when the function () is passed into the variable

  $CL = function ($name) {return
    sprintf (' Hello%s ', name);
  }
  echo $cli (' fuck ')

Called directly by a variable name defined as an anonymous function.

echo Preg_replace_callback (' ~-([A-z]) ~ ', function ($match) {return
  strtoupper ($match [1]);
}, ' Hello-world ' ;`

Using use

$message = ' Hello ';
$example = function () use ($message) {
  var_dump ($message);
Echo $example ();
Output Hello
$message = ' world ';
Output Hello because the value of the inherited variable is the time of the function definition rather than when the function is called
echo $example ();
Reset to Hello
$message = ' Hello ';
Reference
$example = function () use (& $message) {
 var_dump ($message);
Echo $example ();
Output Hello
$message = ' world ';
Echo $example ();
the World//closure function is also used for normal pass values
$message = ' Hello ';
$example = function ($data) use ($message) {return
  "{$data},{$message}";

echo $example (' World ');

Example

Class cart{//Defines constants in the class with the Const keyword, rather than the usual define () function.
  Const Price_butter = 1.00;
  Const PRICE_MILK = 3.00;

  Const PRICE_EGGS = 6.95;
  protected $products = [];
  Public function Add ($product, $quantity) {$this->products[$product] = $quantity; The Public Function getquantity ($product) {//Does the return isset ($this->products[$product]) be defined? $this->products[$
  Product]:false;
    The Public Function gettotal ($tax) {$total = 0.0; $callback = function ($quantity, $product) use ($tax, & $total) {//constant Returns the value of a constant//__class__ the class name $PR

      Ice = constant (__class__. "::P rice_". Strtoupper ($product));
    $total + + ($price * $quantity) * ($tax +1.0);
    }; The Array_walk () function applies a user-defined function to each element in the array.
    In the function, the key name and the key value of the array are parameter Array_walk ($this->products, $callback);

  Callback anonymous function return round ($total, 2);
}} $my _cart = new cart ();
$my _cart->add (' Butter ', 1);
$my _cart->add (' Milk ', 3);


$my _cart->add (' eggs ', 6);
 Print ($my _cart->gettotal (0.05));

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