問題描述

我正在嘗試對數組中的數據運行清理作業，特別是將紀元時間轉換為 YYYY-MM-DD.

我最初嘗試過這個功能:

foreach ($data as $row) {$row['eventdate'] = date('Y-m-d', $row['eventdate']);}echo '
';打印_r($數據);echo '</pre>';
但是，當我輸出數據時，foreach 循環并沒有更新數據.
以下 for 循環確實有效:
for ($i=0; $i
為什么第一個循環失敗而第二個循環成功?他們不一樣嗎?
 解決方案 
當您以目前的方式使用 foreach 循環時，foreach ($data as $row){, $row 被按值"使用，而不是按引用".
嘗試通過將 & 添加到 $row 來更新引用:
foreach ($data as &$row) {$row['eventdate'] = date('Y-m-d', $row['eventdate']);
或者，您可以使用鍵/值方法:
foreach ($data as $index => $row) {$data[$index]['eventdate'] = date('Y-m-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?
 解決方案 
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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