How can PHP error handling and validation be improved in the provided code to enhance security and user experience?

Issue: The provided code does not have proper error handling and validation, which can lead to security vulnerabilities and a poor user experience. To improve this, we can implement error handling to catch and display errors to the user, as well as validate user input to prevent malicious data entry. Code snippet with improved error handling and validation: 

<?php
// Validate and sanitize user input
$username = isset($_POST['username']) ? htmlspecialchars($_POST['username']) : '';
$password = isset($_POST['password']) ? htmlspecialchars($_POST['password']) : '';

// Check for empty fields
if(empty($username) || empty($password)) {
    die("Please enter both username and password.");
}

// Validate username and password format
if(!preg_match("/^[a-zA-Z0-9]{5,}$/", $username) || !preg_match("/^[a-zA-Z0-9!@#\$%^&*()_]{8,}$/", $password)) {
    die("Invalid username or password format.");
}

// Perform authentication logic here

// Error handling
try {
    // Perform authentication logic here
} catch (Exception $e) {
    die("An error occurred: " . $e->getMessage());
}

// Success message
echo "Login successful!";

?>

Keywords

Exception handling filter_var htmlspecialchars error_reporting secure coding

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