为什么我不能用foreach循环更新数组中的数据? [英] Why can't I update data in an array with foreach loop?
问题描述
我试图对数组中的数据执行清理工作,特别是将纪元时间转换为YYYY-MM-DD。
:
foreach($ data as $ row){
$ row ['eventdate'] = date('Ym -d',$ row ['eventdate']);
}
echo'< pre>';
print_r($ data);
echo'< / pre>';
然而,foreach循环没有在输出时更新数据。
以下for循环确实有效:
$ p $ for($ i = 0; $ i< count($ data); $ i ++){
$ data [$ i] ['eventdate'] = date('Ym-d',$ data [$ i] ['eventdate']);
$ b $ p $为什么第一个循环失败,第二个工作呢?它们是不是一样的?
foreach $ c $ ($ data as $ row){
, $ row
正在循环中使用by-value而不是by-reference。试着通过添加&
到 $ row
:
foreach($ data as& amp; ; $ row){
$ row ['eventdate'] = date('Ym-d',$ row ['eventdate']);
或者,您可以使用键/值方法:
foreach($ data as $ index => $ row){
$ data [$ index] ['eventdate'] = date('Ym-d ',$ row ['eventdate']);
I'm trying to run a clean up job on data in an array, specifically converting epoch time to YYYY-MM-DD.
I tried this function originally:
foreach ($data as $row) {
$row['eventdate'] = date('Y-m-d', $row['eventdate']);
}
echo '<pre>';
print_r($data);
echo '</pre>';
However the foreach loop didn't update the data when I output it.
The following for loop did work:
for ($i=0; $i<count($data); $i++) {
$data[$i]['eventdate'] = date('Y-m-d', $data[$i]['eventdate']);
}
Why did the first loop fail and the second work? Aren't they the same?
When you're using a foreach
loop in the way you currently are, foreach ($data as $row) {
, $row
is being used "by-value", not "by-reference".
Try updating to a reference by adding the &
to the $row
:
foreach ($data as &$row) {
$row['eventdate'] = date('Y-m-d', $row['eventdate']);
Or, you can use the key/value method:
foreach ($data as $index => $row) {
$data[$index]['eventdate'] = date('Y-m-d', $row['eventdate']);
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