What are the potential consequences of using outdated functions like mysql_query in PHP?

Using outdated functions like mysql_query in PHP can lead to security vulnerabilities such as SQL injection attacks, as these functions do not support prepared statements. To solve this issue, it is recommended to use modern functions like mysqli_query or PDO with prepared statements to prevent SQL injection attacks and ensure better security for your application. 

// Connect to the database using mysqli
$mysqli = new mysqli("localhost", "username", "password", "database");

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

// Prepare a SQL statement with a placeholder
$stmt = $mysqli->prepare("SELECT * FROM users WHERE username = ?");

// Bind parameters
$stmt->bind_param("s", $username);

// Execute the statement
$stmt->execute();

// Get the result
$result = $stmt->get_result();

// Fetch data
while ($row = $result->fetch_assoc()) {
    // Process the data
}

// Close the statement and connection
$stmt->close();
$mysqli->close();

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