PHP/PDO-使用多个foreach循环时，请多次使用PDO语句 [英] PHP / PDO - Use PDO statement multiple times when using multiple foreach loops

问题描述

我有以下代码:

if(!empty($postCountryAdd)) {
$sqlQueryLocalityAdd = $dbh->prepare("SELECT DISTINCT locality_add FROM table WHERE country_add = :country_add ORDER BY locality_add ASC");
$sqlQueryLocalityAdd->execute(array(':country_add' => $postCountryAdd));

echo '<option value="">Select locality</option>';
    foreach($sqlQueryLocalityAdd as $localityAddRow) {
        //while ($localityAddRow = $sqlQueryLocalityAdd->fetch()){
        echo '<option value="';
        echo $localityAddRow["locality_add"];
        echo '">';
        echo $localityAddRow["locality_add"];
        echo '</option>';
    }
}

如果我使用foreach($sqlQueryLocalityAdd as $localityAddRow)，代码将停止响应.为什么我不能多次使用foreach?我该如何解决?

If I use foreach($sqlQueryLocalityAdd as $localityAddRow) the code stops responding. Why can't I use foreach more than once? How can I fix it please?

推荐答案

$sqlQueryLocalityAdd不是结果集，它是一个PDOStatement对象，您只能直接对其进行一次迭代(如deceze所清楚指出的).

$sqlQueryLocalityAdd isn't a result set, it's a PDOStatement object and you can only iterate over it directly once (as noted clearly by deceze).

execute()语句在查询成功时返回boolean true或false.

The execute() statement returns a boolean true or false on success of the query.

如果成功运行，则需要在查询后从中获取结果并迭代返回的数组:

If successfully run, you need to fetch results from it post-query and iterate the array returned:

   $success = $sqlQueryLocalityAdd->execute(array(':country_add' => $postCountryAdd));
   if($success) {

       $results = $sqlQueryLocalityAdd->fetchAll();

       foreach($results as $localityAddRow) {
           echo '<option value="';
            ....

生成的数组$results只是一个普通数组，因此您可以根据需要对其进行多次迭代.

The resulting array $results is just a vanilla array, so you can iterate over it as many times as you want.

注意:如果execute()返回false，则查询有问题-成功运行的查询返回空结果集结果仍将导致true.

Note: If the execute() returns false, something is wrong with the query--a successful running query returning a empty result set results will still result in a true.

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