How to understand closure bind and bindto in PHP

Bind is a static version of BindTo, so just say bind. (not too much to know why to make two versions)

Official document: Copy a closure that binds the specified $this object and class scope.

In fact, the latter half of the sentence is not clear. My understanding: The method of converting a closure into a class (this method does not need to be called by the object), so that the $this, static, self in the closure are converted to the corresponding object or class.

Because there are several situations:

1. Bind only $this objects.
2. Bind the class scope only.
3. Bind $this objects and class scopes at the same time. (the document says)
4, are not bound. (Such a dozen is purely copy, the documentation is used cloning instead of bind or bindto)

Here's a detailed explanation of the following:

1. Bind only $this objects

$closure = function ($name, $age) {    $this->name = $name;    $this->age = $age;}; Class Person {public    $name;    public $age;    Public function Say () {        echo ' My name is {$this->name}, I ' m {$this->age} years old.\n ";    }} $person = new Person (),//Bind $this in $closure to $person//so that setting name and age in $bound_closure is actually setting $person name and age// That is, the specified $this object ($person) is bound $bound _closure = Closure::bind ($closure, $person); $bound _closure (' php '); $person Say ();

　　

My name is PHP, I ' m years-old.

Note: In this example above, it is not possible to use static in $closure, if you need to use static, pass the third argument to the class name with the namespace.

2. Bind the class scope only.

$closure = function ($name, $age) {  static:: $name =  $name;  Static:: $age = $age;}; Class Person {    static $name;    static $age;    public static function say ()    {        echo ' My name is '. Static:: $name. ", I ' m". Static:: $age. "Years old.\n";    }} Bind the static in the $closure to the person class//So when you set name and age in $bound_closure, you actually set the name and age//of the person to bind the specified static (person) $ Bound_closure = Closure::bind ($closure, NULL, Person::class), $bound _closure (' php ', 100); Person::say ();

　　

My name is PHP, I ' m years-old.

Note: In the above example, it is not possible to use $this in $closure because our bind binds only the class name, which is static, if you need to use $this, a new object is passed in as the second parameter of BIND.

3. Bind $this objects and class scopes at the same time. (the document says)

$closure = function ($name, $age, $sex) {    $this->name = $name;    $this->age = $age;    Static:: $sex = $sex;}; Class Person {public    $name;    public $age;    static $sex;    Public function say ()    {        echo "My name is {$this->name}, I ' m {$this->age} years old.\n";        echo "Sex:". Static:: $sex. ". \ n";    }} $person = new Person (),//The static in $closure is bound to the person class, $this bound to $person object $bound_closure = Closure::bind ($closure, $ person, person::class); $bound _closure (' php ', ' female '); $person->say ();

　　

My name is PHP, I ' m years-old. Sex:female.

In this example, you can use both $this and static in $closure

4, are not bound. (Such a dozen is purely copy, the documentation is used cloning instead of bind or bindto)

$closure = function () {    echo "bind nothing.\n";};/ /With $bound_closure = Clone $closure; $bound_closure = Closure::bind ($closure, null); $bound _closure ();

　　

Bind nothing.

This is the right clone.

How to understand closure bind and bindto in PHP