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Regarding closure anonymous functions, a very typical problem in JS
is to bind it to a this
scope. In fact, this problem also exists in PHP
, such as the following code:
$func = function($say){ echo $this->name, ':', $say, PHP_EOL; }; $func('good'); // Fatal error: Uncaught Error: Using $this when not in object context
In this anonymous function, we use $this->name
To get the $name
attribute under the current scope, but who is this $this
? We have not defined it, so an error will be reported directly here. The error message is: $this
is used but there is no object context, that is, the scope of the $this reference is not specified.
1.bindTo() method binding $this
$func = $func->bindTo($lily, 'Lily'); // $func = $func->bindTo($lily, Lily::class); // $func = $func->bindTo($lily, $lily); $func1('cool');
This time you can output normally. bindTo()
The method is to copy a current closure object and then bind it to the $this
scope and class scope.
The $lily parameter is a object $newthis
parameter, which is to specify $this
for this copied anonymous function.
'Lily' binds a new class scope, which represents a type and determines which private and protected methods can be called in this anonymous function
If this parameter is not given, then we cannot access the $name
attribute of this private
:
$func1 = $func->bindTo($lily); $func1('cool2'); // Fatal error: Uncaught Error: Cannot access private property Lily::$name
2.call() method binding $this
$func->call($lily, 'well'); // Lily:well
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