Secure MySQL Join Queries in PHP Using Prepared Statements | PHP MySQLi Example

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In this article, we’ll provide a real-world example of fetching related data from multiple tables. We will use JOIN and prepared statements in PHP.

PHP MySQL Join Queries Prepared Statement

$review_id = 1;
$user_id = 1;

$stmt = $connect->prepare("
    SELECT n.id AS notification_id, n.reply_at, r.comment, r.rating,
           p.product_image, u.name AS username
    FROM tbl_notification n
    JOIN tbl_reviews r ON n.review_id = r.review_id
    JOIN tbl_product p ON r.product_id = p.product_id
    JOIN tbl_user u ON n.user_id = u.id
    WHERE n.review_id = ? AND n.user_id = ?
");

$stmt->bind_param("ii", $review_id, $user_id);
$stmt->execute();
$result = $stmt->get_result();

while ($row = $result->fetch_assoc()) {
    print_r($row);
}

Step-by-Step Explanation for beginners:

For Beginners who are learning the development, description is made.Then they will understand what is going on Step by Step.

1. Define Variables

$review_id = 1;
$user_id = 1;

These variables store the demo IDs for the review and user.  You can add GET /POST method for fetching IDs

2. Create a Prepared Statement

$stmt = $connect->prepare("
    SELECT n.id AS notification_id, n.reply_at, r.comment, r.rating,
           p.product_image, u.name AS username
    FROM tbl_notification n
    JOIN tbl_reviews r ON n.review_id = r.review_id
    JOIN tbl_product p ON r.product_id = p.product_id
    JOIN tbl_user u ON n.user_id = u.id
    WHERE n.review_id = ? AND n.user_id = ?");

The ? placeholders make the query safe from SQL Injections.

3. Bind Parameters

$stmt->bind_param("ii", $review_id, $user_id);

The “ii” means two integers are being bound to the query. If you find with string key then you can use

$stmt->bind_param('si', $stringKey, $user_id);

4. Execute the Query

$stmt->execute();

5. Fetch the Results and Print

while ($row = $result->fetch_assoc()) {
    print_r($row);
}