What best practices should be followed when writing PHP scripts that involve querying and displaying data from different database tables?

When writing PHP scripts that involve querying and displaying data from different database tables, it is important to use prepared statements to prevent SQL injection attacks. Additionally, it is recommended to sanitize user input and validate data before executing queries to ensure data integrity. Lastly, consider using JOIN statements to efficiently retrieve data from multiple tables in a single query. 

<?php
// Connect to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// Prepare and execute a query to retrieve data from multiple tables using a JOIN statement
$sql = "SELECT users.username, orders.order_id FROM users INNER JOIN orders ON users.user_id = orders.user_id";
$result = $conn->query($sql);

// Display the results
if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "Username: " . $row["username"]. " - Order ID: " . $row["order_id"]. "<br>";
    }
} else {
    echo "0 results";
}

// Close the connection
$conn->close();
?>

Keywords

SQL injection PDO prepared statements data validation database normalization

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