How can the use of deprecated functions like mysql_select_db and mysql_query in PHP code impact the performance and security of a login script?

Using deprecated functions like mysql_select_db and mysql_query in PHP code can impact performance and security of a login script as these functions are no longer recommended for use and may have vulnerabilities. To address this issue, it is recommended to use the mysqli or PDO extension for database operations in PHP. 

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

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

// Perform query using prepared statement
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->bind_param("ss", $username, $password);

$username = "user123";
$password = "pass123";
$stmt->execute();

// Check if user exists
$result = $stmt->get_result();
if ($result->num_rows > 0) {
    // User authenticated successfully
    echo "Login successful";
} else {
    // User authentication failed
    echo "Login failed";
}

$stmt->close();
$conn->close();
?>

Keywords

deprecated functions mysql_select_db mysql_query performance impact security risk

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