PHP，如果其他语句不能正常工作

Question

I have a php if else statement which checks if the query contains a string. if it doesn't it will output a style-sheet. If it contains a string it will get the users style-sheet. However it seems to only be outputting the 1st fixed style-sheet apposed to the users set one.

 <?php $user_data_load = $con->query("SELECT theme FROM users WHERE id = '".$_SESSION['user']['id']."'");?> <?php if (!isset($user_data_load) or !is_array($user_data_load) or empty($user_data_load)): ?> <link id="stylesheet" rel="stylesheet" href="css/theme_default.css" type='text/css'> <?php else: ?> <?php while($userloaded = $user_data_load->fetch_object()): ?> <link id='stylesheet' rel='stylesheet' href='<?= $userloaded->theme?>' type='text/css'> <?php endwhile;?> <?php endif;?> 

Answer 1

Some notes to your if:

if (!isset($user_data_load) or !is_array($user_data_load) or empty($user_data_load)): ?>

!isset($user_data_load) will always be false. isset checks if a variable is set, and since you set it yourself, it will always return true, it doesn't matter whats in that variable.

!is_array($user_data_load) will always be true, because $con->query never returns a array, therefore you'll always use the default stylesheet.

Try it like this:

<?php

$stmt = $con->prepare("SELECT theme
        FROM users
        WHERE id = ?");
$stmt->bind_param('i', $_SESSION['user']['id']);
$stmt->execute();

if ($data = $stmt->get_result()->fetch_object()) {
    echo '<link id="stylesheet" rel="stylesheet" href="' . $data->theme . '" type="text/css">';
} else {
    echo '<link id="stylesheet" rel="stylesheet" href="css/theme_default.css" type="text/css">';
}

Answer 2

Every id will be 'stylesheet'. Take out the id to prevent rebinding.

<link rel='stylesheet' href='<?= $userloaded->theme?>' type='text/css'>