Let's go deeper into the foreach loop and unset() function. Let the master explain it to me.

<code>   foreach($arr as $key=>$val){
        if(in_array($val,$pattern)){
            unset($arr[$key]);
             break;
        }
    }   
    
     foreach($arr as $key=>$val){
        if(in_array($val,$pattern)){
            unset($val);
             break;
        }
    }
    
    
    贴了部分代码，我就想问一下unset()函数时，为什么是unset($arr[$key]);而不是unset($val);不知道懂不懂我的意思</code>

Reply content:

<code>   foreach($arr as $key=>$val){
        if(in_array($val,$pattern)){
            unset($arr[$key]);
             break;
        }
    }   
    
     foreach($arr as $key=>$val){
        if(in_array($val,$pattern)){
            unset($val);
             break;
        }
    }
    
    
    贴了部分代码，我就想问一下unset()函数时，为什么是unset($arr[$key]);而不是unset($val);不知道懂不懂我的意思</code>

Let me briefly explain the difference:

unset($arr[$key]) //What is destroyed is an element in the $arr array

unset($val) //When destroyed, the variable $val is an element in $arr, which is equivalent to reopening a variable. Destroying the reopened variable will not affect the original array $arr. .

I wonder if you have any questions?

<code>foreach($arr as $key=>$value)
{    
    $key和$value //这里是重新初始化的一个全新的变量,和 $arr 无关
}</code>