array_map回調(diào)函數(shù)內(nèi)部變量作用域分享

rozbo 發(fā)布于2019-06-28 18:36 / 2424人閱讀

摘要：修宇拉拉拉棟浩吼吼吼上線哲哈哈哈帥奇喵喵喵如上目的為在回調(diào)用使變量自增經(jīng)測除函數(shù)內(nèi)部變量只被一次其余類的屬性均無此作用域問題無該作用域問題想來原理很簡單這里用的是匿名回調(diào)函數(shù)回調(diào)函數(shù)的層級(jí)本就與方法應(yīng)相同只不過匿名閉包使回調(diào)函數(shù)

num = 0; //test3
    }
    
    public function fun()
    {
        $arr = array(
            array("people" => "修宇","hobby" => "拉拉拉"),
            array("people" => "棟浩","hobby" => "吼吼吼"),
            array("people" => "上線哲","hobby" => "哈哈哈"),
        );
        $people = "帥奇";
        $hobby = "喵喵喵";
        
        $num = 0;    //test1
        
        // $this->num = 0; //test2
        
        $arr = array_map(function($v) use($people, $hobby){
            $num++; //test1
            // $this->num++;    //test2345
            $v["people"] = $people.$num;
            $v["hobby"] = $hobby.$num;   //test1   
            
            // $v["people"] = $people.$this->num;
            // $v["hobby"] = $hobby.$this->num;    //test2 or test3 or test4 or test5 or test6
            return $v;
        },$arr);
        // return $arr;
        
        foreach($arr as $v) {
            $num++;
            $v["people"] = $people.$num;
            $v["hobby"] = $hobby.$num;
        }
        return $arr;
    }
}
$test = new Test();
var_dump($test->fun());
?>

如上code 目的為在回調(diào)用使變量自增 , 經(jīng)測除fun函數(shù)內(nèi)部變量只被++一次其余類的屬性均無此作用域問題！
foreach 無該作用域問題 !
想來原理很簡單這里array_map用的是匿名回調(diào)函數(shù) . 回調(diào)函數(shù)的層級(jí)本就與fun方法應(yīng)相同 , 只不過匿名閉包使回調(diào)函數(shù)寫在array_map中.
$num變量為fun函數(shù)內(nèi)部變量 , 其作用域再fun函數(shù)內(nèi). 綜上所述回調(diào)函數(shù)與fun函數(shù)同級(jí). 故$num并不作用在回調(diào)函數(shù)內(nèi). 故無法自增.
同理類的屬性作用域即在fun函數(shù)也在回調(diào)函數(shù) !

回調(diào)非匿名使用場景原理如下 :

num = 0; //test3
    }
    
    public function callBack($v, $rV) {
        $this->num++;
        $v["people"] = $rV["people"].$this->num;
        $v["hobby"] = $rV["hobby"].$this->num;
        return $v;
    }
    
    public function fun()
    {
        $arr = array(
            array("people" => "修宇","hobby" => "拉拉拉"),
            array("people" => "棟浩","hobby" => "吼吼吼"),
            array("people" => "上線哲","hobby" => "哈哈哈"),
        );
    
        $num = 0;    //test1
       
        $replace = array(
            array("people" => "帥奇", "hobby" => "喵喵喵"),
            array("people" => "帥奇", "hobby" => "喵喵喵"),
            array("people" => "帥奇", "hobby" => "喵喵喵"),
        );
        $arr = array_map(array($this,"callBack"),$arr, $replace);
        return $arr;
    }
}
$test = new Test();
var_dump($test->fun());
?>

上述array_map函數(shù)想傳計(jì)數(shù)器都不好傳 , 于是使用array_walk
array_walk 類的屬性

num = 0; //test3
    }
    
    public function callBack($v, $k) {
        $this->num++;
        var_dump($this->num.":".$k."=>".$v);
    }
    
    public function fun()
    {
        $arr = array("people" => "修宇","hobby" => "拉拉拉");
        array_walk($arr, array($this,"callBack"));
    }
}
$test = new Test();
$test->fun();
?>

array_walk fun函數(shù)內(nèi)的局部變量 :

".$v);
    }
    
    public function fun()
    {
        $arr = array("people" => "修宇","hobby" => "拉拉拉");
        
        $num = 0;
        
        array_walk($arr, array($this, "callBack"), $num);
    }
}
$test = new Test();
$test->fun();
?>

由array_walk fun函數(shù)內(nèi)的局部變量情況就引發(fā)array_walk、和array_map底層實(shí)現(xiàn)的探究
※很多帖子說array_walk與foreach一樣 , 這么看不一樣 . 使用時(shí)要注意 !