更改 foreach 循环内的值不会更改正在迭代的数组中的值

问题描述

为什么会这样:

foreach( $store as $key => $value){
$value = $value.".txt.gz";
}

unset($value);

print_r ($store);

Array
(
[1] => 101Phones - Product Catalog TXT
[2] => 1-800-FLORALS - Product Catalog 1
)

我正在尝试获取 101Phones - 产品目录 TXT.txt.gz

I am trying to get 101Phones - Product Catalog TXT.txt.gz

对正在发生的事情的想法?

Thoughts on whats going on?

好吧，我找到了解决方案……我的数组中的变量有我看不到的值……正在做

Alright I found the solution...my variables in my array had values I couldn't see...doing

$output = preg_replace('/[^(x20-x7F)]*/','', $output);
echo($output);

清理并使其正常工作

推荐答案

文档 http://php.net/manual/en/control-structures.foreach.php 清楚地说明了您遇到问题的原因:

The doc http://php.net/manual/en/control-structures.foreach.php clearly states why you have a problem:

为了能够在循环中直接修改数组元素，在 $value 前面加上 &.在这种情况下，值将通过引用赋值."

"In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference."

<?php
$arr = array(1, 2, 3, 4);
foreach ($arr as &$value) {
    $value = $value * 2;
}
// $arr is now array(2, 4, 6, 8)
unset($value); // break the reference with the last element
?>

只有当迭代数组可以被引用(即如果它是一个变量)时，才可能引用 $value.以下代码不起作用:

Referencing $value is only possible if the iterated array can be referenced (i.e. if it is a variable). The following code won't work:

<?php
/** this won't work **/
foreach (array(1, 2, 3, 4) as &$value) {
    $value = $value * 2;
}
?>

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