替换foreach循环中的数组值

Question

我在这里做错了什么？这很简单，我忽略了一些东西。我试图在foreach循环中替换数组键的值：

$arr = array();
$arr['firstimg'] = '123';
$arr['secondimg'] = '456';
$arr['thirdimg'] = '789';

foreach ($arr as $key => $value) {

    if ($key == 'secondimg') { 
      $value = '000';

    } 

}

print_r($arr);

阵列保持不变。

Answer 1

变量$value的范围限定为循环。您需要更新$arr[$key]。

的值

或者，您可以按如下方式声明循环：

foreach ($arr as $key => &$value) {

这使$value引用了原始数组值（而不是副本）。

Answer 2

应该是：

foreach ($arr as $key => $value) {

    if ($key == 'secondimg') { 
      $arr['secondimg'] = '000';

    } 

}

Answer 3

通过引用传递，

$arr = array();
$arr['firstimg'] = '123';
$arr['secondimg'] = '456';
$arr['thirdimg'] = '789';

foreach ($arr as $key => $value) {

    if ($key == 'secondimg') { 
      $value = '000';

    } 

}

print_r($arr);

到

$arr = array();
$arr['firstimg'] = '123';
$arr['secondimg'] = '456';
$arr['thirdimg'] = '789';

foreach ($arr as $key => &$value) {

    if ($key == 'secondimg') { 
      $value = '000';

    } 

}

print_r($arr);