PHP User Registration Form with Password Validation

• ☆ This PHP script implements a secure user registration form with MySQL integration and server-side password validation.
• ☆ It checks whether the submitted password contains at least one letter, one number, and one special character.
• ☆ If all conditions are met, the password is hashed and the user is stored in the database.

	
	<?php  
	require 'db.php';
	
	$errorList = [];
	$success = "";
	$username = "";  // store input username
	
	if ($_SERVER["REQUEST_METHOD"] == "POST") {
	
	    $username = htmlspecialchars($_POST["username"]);
	    $password = htmlspecialchars($_POST["password"]);
	
	    // Server-side password validation conditions
	    $conditions = [
	        'letter' => [
	            'pattern' => '/[A-Za-z]/',
	            'message' => 'Password must contain at least one letter.'
	        ],
	        'number' => [
	            'pattern' => '/[0-9]/',
	            'message' => 'Password must contain at least one number.'
	        ],
	        'special' => [
	            'pattern' => '/[\W_]/',
	            'message' => 'Password must contain at least one special character.'
	        ]
	    ];
	
	    $valid = true;
	    foreach ($conditions as $key => $rule) {
	        if (!preg_match($rule['pattern'], $password)) {
	            $errorList[$key] = false;
	            $valid = false;
	        } else {
	            $errorList[$key] = true;
	        }
	    }
	
	    if ($valid) {
	        // Hash and store password
	        $hashed = password_hash($password, PASSWORD_DEFAULT);
	        $stmt = $conn->prepare("INSERT INTO users (username, password) VALUES (?, ?)");
	        $stmt->bind_param("ss", $username, $hashed);
	
	        try {
	            $stmt->execute();
	            $success = "✅ Registered successfully!";
	            $username = "";  // clear the username field
	            $errorList = []; // clear errors after success
	        } catch (mysqli_sql_exception $e) {
	            if (str_contains($e->getMessage(), 'Duplicate entry')) {
	                $errorList['duplicate'] = "❌ Username already taken.";
	            } else {
	                $errorList['unknown'] = "❌ Something went wrong. Please try again.";
	            }
	        }
	    }
	}
	?>
	
	<link rel="stylesheet" href="style.css">
	<style>
	    .error-msg { color: red; font-size: 0.9em; margin-top: 5px; }
	    .success-msg { color: green; font-size: 1em; margin-bottom: 10px; }
	    .check { color: green; }
	    .cross { color: red; }
	</style>
	
	<form method="post">
	    <h2>Register</h2>
	
	   <?php
		if (!empty($success)) {
		    echo '<div class="success-msg">' . htmlspecialchars($success) . '</div>';
		}
	   ?>
	
	    Username: 
	    <input name="username" value="<?= htmlspecialchars($username) ?>" required><br>
	
	    Password: 
	    <input type="password" name="password" required><br><br>
	
	    <!-- Show password rules -->
	    <?php
		if ($_SERVER["REQUEST_METHOD"] == "POST" && empty($success)) {
		?>
		    <div>
		        <p>Password must meet the following conditions:</p>
		        <ul style="list-style: none; padding-left: 0;">
		            <li>
		                <?php echo (isset($errorList['letter']) && $errorList['letter']) ? '✅' : '❌'; ?>
		                At least one letter
		            </li>
		            <li>
		                <?php echo (isset($errorList['number']) && $errorList['number']) ? '✅' : '❌'; ?>
		                At least one number
		            </li>
		            <li>
		                <?php echo (isset($errorList['special']) && $errorList['special']) ? '✅' : '❌'; ?>
		                At least one special character
		            </li>
		        </ul>
		    </div>
		<?php
		}
	   ?>

	
	    <!-- Username errors -->
	    <?php
		if (isset($errorList['duplicate'])) {
		    echo '<div class="error-msg">' . htmlspecialchars($errorList['duplicate']) . '</div>';
		} elseif (isset($errorList['unknown'])) {
		    echo '<div class="error-msg">' . htmlspecialchars($errorList['unknown']) . '</div>';
		}
	    ?>
	
	    <button type="submit">Register</button>
	</form>
	

Password Validation Example in W3School

How TO - Password Validation