Question

我有这个查询

$categories = $dbh->query(" SELECT * FROM categories ORDER BY name ASC ");

我需要在这个数组上循环两次。

foreach($categories as $category) {
    dd($category);
}
echo '---------------';
foreach($categories as $category) {
    dd($category);
}

此代码返回

stdClass Object
(
    [id] => 24
    [name] => granchi
    [slug] => granchi
)
stdClass Object
(
    [id] => 26
    [name] => molluschi
    [slug] => molluschi
)
stdClass Object
(
    [id] => 25
    [name] => pesci
    [slug] => pesci
)
---------------

在第二个循环中，数组变空。我发现了类似的问题Two While Loops, Second Returns Empty Array?，但我没有为PDO找到类似的解决方案。

如果没有查询两次创建两个相同的数组，我该如何循环它们两次？

我不明白为什么它会在第一次循环后清空。

Answer 1

您必须先将查询结果提取到数组中。

的mysqli：

<?php

$db = new mysqli('localhost', 'root', '', 'test');

if($db->connect_errno > 0){
    die('Unable to connect to database [' . $db->connect_error . ']');
}

$sql = " SELECT * FROM categories ORDER BY name ASC ";

if(!$result = $db->query($sql)){
    die('There was an error running the query [' . $db->error . ']');
}

while($row = $result->fetch_assoc()){
    echo $row['**column name**'] . '<br />';
}

?>

PDO：

<?php

$db = new PDO('mysql:host=localhost;dbname=test;charset=utf8', 'root', '');

$sql = "SELECT * FROM categories ORDER BY name ASC ";

try {
    $stmt = $db->query($sql);
} catch(PDOException $ex) {
    echo "An Error occured!";
}

$result = $stmt->fetch(PDO::FETCH_ASSOC);

foreach($result as $key => $val)
    {
    echo $key.' - '.$val.'<br />';
    }

?>

PHP：在foreach（）循环后数组变空

1 个答案: