php foreach pointer-PHP Tutorial-php.cn

php foreach pointer

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Release： 2016-08-18 09:16:24

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$arr = array('a', 'b', 'c');
$i = 0;
foreach($arr as $key => $value) {

<code>if($i == 0) {
    //第一次就执行了写操作
    $arr[$key] = $value . $value;
}
$i++;</code>

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}
//The pointer of $arr has been moved once, pointing to the second element b.
var_dump(current($arr));//b

Why does the pointer go to the second element at the beginning

Reply content:

$arr = array('a', 'b', 'c');
$i = 0;
foreach($arr as $key => $value) {

<code>if($i == 0) {
    //第一次就执行了写操作
    $arr[$key] = $value . $value;
}
$i++;</code>

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}
//The pointer of $arr has been moved once, pointing to the second element b.
var_dump(current($arr));//b

Why does the pointer go to the second element at the beginning

<code>$arr = array('a', 'b', 'c');
$i = 0;
foreach($arr as $key => $value) {
    if($i == 0) {
        $arr[$key] = $value . $value;
    }
    $i++;
}

</code>

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The pseudocode is the same

<code>$arr = array('a', 'b', 'c');
$i = 0;
$arrCopy = $arr; //复制出一个待循环数组的副本，接下来都是操作这个副本
$key = currentKey($arrCopy); //将获取到的值分配给$k;
$val = currentVal($arrCopy); //将获取到的值分配给$v;

//移动副本数组的指针,这边执行顺序比写时复制高，所以先移动
next($arrCopy);
$arr = $arrCopy;//将副本赋值回给$arr（（主要是将指针同步移动））

{ //大括号的内容
    if($i == 0) {
        $arr[$key] = $value . $value;
    }
    $i++;
}


//然后第二次循环
$key = currentKey($arrCopy); 
$val = currentVal($arrCopy);
//移动副本数组的指针,这边执行顺序比写时复制高，所以先移动
next($arrCopy);
$arr = $arrCopy;//将副本赋值回给$arr（（主要是将指针同步移动））

{ //大括号的内容
    if($i == 0) {
        $arr[$key] = $value . $value;
    }
    $i++;
}
//然后第三次循环
$key = currentKey($arrCopy); 
$val = currentVal($arrCopy);
//移动副本数组的指针,这边执行顺序比写时复制高，所以先移动
next($arrCopy);
$arr = $arrCopy;//将副本赋值回给$arr（（主要是将指针同步移动））

{ //大括号的内容
    if($i == 0) {
        $arr[$key] = $value . $value;
    }
    $i++;
}</code>

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