尝试使用foreach循环使用MYSQL选择一行数据

Question

Im trying to make a simple friend system with PHP & MYSQL and I don't know if it's even possible to get use data from another table with just their id. I am very new by the way so I don't know the language very well :) Any help would be very much valued

<?php if(count($friend_request) > 0): ?>
    <?php foreach ($friend_request as $friend_request): ?>
        <?php
            try{
                $statement = $db->query("SELECT * FROM users WHERE id = '$friend_request['id']' ");
                $user_info = $statement->fetchAll(PDO::FETCH_ASSOC);

            }catch (PDOException $ex){
                $user_info = flashMessage("An error occurred: " .$ex->getMessage());
            }   

        ?>
        <?=$friend_request['id'] ?>
        <?=$friend_request['user_requested'] ?>
        <?=$friend_request['user_to'] ?>
        <?=$friend_request['request_date'] ?>
    <?php endforeach; ?>
<?php else: ?>
    <center>
        <input id="emailInput" type="text" name="requestEmail" placeholder="[e-mail]">
    </center>
<?php endif; ?>

Answer 1

You need to use curly syntax if you want to put a quoted string in the index of a variable inside a string.

$statement = $db->query("SELECT * FROM users WHERE id = '{$friend_request['id']}' ");

You can also leave the quotes out of the index, but that's not my preference.

But it would be better to use a prepared statement.

<?php
if(count($friend_request) > 0):
    $statement = $db->prepare("SELECT * FROM users WHERE id = :id ");
    foreach ($friend_request as $friend_request):
        try{
            $statement->execute([':id' => $friend_request['id']]);
            $user_info = $statement->fetchAll(PDO::FETCH_ASSOC);
        }catch (PDOException $ex){
            $user_info = flashMessage("An error occurred: " .$ex->getMessage());
        }   
        ?>
        <?=$friend_request['id'] ?>
        <?=$friend_request['user_requested'] ?>
        <?=$friend_request['user_to'] ?>
        <?=$friend_request['request_date'] ?>
    <?php endforeach; ?>
<?php else: ?>
    <center>
        <input id="emailInput" type="text" name="requestEmail" placeholder="[e-mail]">
    </center>
<?php endif; ?>