Detailed usage methods in PHP closure function() use()

PHP’s closure (Closure) is also anonymous function. It was introduced in PHP5.3.

The syntax of closure is very simple. The only keyword that needs attention is use. Use means to connect the closure with external variables.

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$a =function()use($b) {  
}

Several functions of closure:

1 Reduce the code of foreach loop

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products[$product] = $quantity;  
    }  
    public function getQuantity($product)  
    {  
        return isset($this->products[$product]) ? $this->products[$product] :  
               FALSE;  
    }  
    public function getTotal($tax)  
    {  
        $total = 0.00;  
        $callback =  
            function ($quantity,$product)use ($tax, &$total)  
            {  
                $pricePerItem = constant(CLASS ."::PRICE_" .  
                    strtoupper($product));  
                $total += ($pricePerItem *$quantity) * ($tax + 1.0);  
            };  
        array_walk($this->products,$callback);  
        return round($total, 2);;  
    }  
}  
$my_cart =new Cart;  
// 往购物车里添加条目  
$my_cart->add('butter', 1);  
$my_cart->add('milk', 3);  
$my_cart->add('eggs', 6);  
// 打出出总价格，其中有 5% 的销售税.  
print $my_cart->getTotal(0.05) . "\n";  
// The result is 54.29  
?>

If we transform the getTotal function here, we must use foreach

2 Reduce function parameters

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function html ($code ,$id="",$class=""){  
if ($id !=="")$id =" id = \"$id\"" ;  
$class = ($class !=="")?" class =\"$class\"":">";  
$open ="<$code$id$class";  
$close ="";  
return function ($inner ="")use ($open,$close){  
return "$open$inner$close";};  
}

If we use the usual method, we will put the inner into the html function parameters , so that whether it is code reading or use It’s better to use closure

3 Unlock the recursive function

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 Note that use in the above question uses &, if you don’t use & here, an error will occur n-1) Yes The function cannot be found (the type of fib was not defined before)
So when you want to use a closure to cancel the loop function, you need to use the form 
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4 About Delayed binding
If you need to delay binding the variables in use, you need to use references, otherwise a copy will be made and placed in use when defined
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Use references And not using references means assignment when calling or assigning when declaring 
The above is the detailed usage method of PHP closure function() use() that I compiled for everyone. I hope it will be helpful to everyone in the future. help. 
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