How can PHP developers effectively troubleshoot and debug login scripts that are not functioning as expected?

Issue: When login scripts are not functioning as expected, PHP developers can effectively troubleshoot and debug by checking for errors in the code, ensuring that all variables are being properly passed and handled, verifying the database connection, and testing the login functionality step by step. 

<?php
// Check for errors in the code
error_reporting(E_ALL);
ini_set('display_errors', 1);

// Ensure variables are properly passed and handled
$username = $_POST['username'];
$password = $_POST['password'];

// Verify the database connection
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

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

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

// Test the login functionality step by step
$sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Login successful
    echo "Login successful!";
} else {
    // Login failed
    echo "Login failed. Please try again.";
}

$conn->close();
?>

Keywords

PHP debugging troubleshooting login scripts error handling

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