php 匿名函数的一些用法示例

<?php
echo  preg_replace_callback ( '~-([a-z])~' , function ( $match ) {
    return  strtoupper ( $match [ 1 ]);
},  'hello-world' );
// 输出 helloWorld
?>

<?php
$greet  = function( $name )
{
     printf ( "Hello %s\r\n" ,  $name );
};

$greet ( 'World' );
$greet ( 'PHP' );
?>

<?php
$message  =  'hello' ;

// 没有 "use"
$example  = function () {
     var_dump ( $message );
};
echo  $example ();

// 继承 $message
$example  = function () use ( $message ) {
     var_dump ( $message );
};
echo  $example ();

// Inherited variable's value is from when the function
// is defined, not when called
$message  =  'world' ;
echo  $example ();

// Reset message
$message  =  'hello' ;

// Inherit by-reference
$example  = function () use (& $message ) {
     var_dump ( $message );
};
echo  $example ();

// The changed value in the parent scope
// is reflected inside the function call
$message  =  'world' ;
echo  $example ();

// Closures can also accept regular arguments
$example  = function ( $arg ) use ( $message ) {
     var_dump ( $arg  .  ' '  .  $message );
};
$example ( "hello" );
?>

Notice: Undefined variable: message in /example.php on line 6
NULL
string(5) "hello"
string(5) "hello"
string(5) "hello"
string(5) "world"
string(11) "hello world"

<?php
// 一个基本的购物车，包括一些已经添加的商品和每种商品的数量。
// 其中有一个方法用来计算购物车中所有商品的总价格，该方法使
// 用了一个 closure 作为回调函数。
class  Cart
{
    const  PRICE_BUTTER   =  1.00 ;
    const  PRICE_MILK     =  3.00 ;
    const  PRICE_EGGS     =  6.95 ;

    protected    $products  = array();
    
    public function  add ( $product ,  $quantity )
    {
         $this -> 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" ;
// 最后结果是 54.29
?>