php pdo checkboxes insert

[ianhaney]

Hi

I am trying to add checkboxes to a registration form I am doing for a client and need to add multiple checkbox values to a database using php and pdo but am not 100% on pdo and know I done it wrong as I get the following error when clicking the submit button

SQLSTATE[HY093]: Invalid parameter number: parameter was not defined

Below is my code

			//insert into database with a prepared statement
			$stmt = $db->prepare('INSERT INTO members (username,password,email,drivers,active) VALUES (:username, :password, :email, :drivers, :active)');
			$stmt->execute(array(
				':username' => $_POST['username'],
				':password' => $hashedpassword,
				':email' => $_POST['email'],	
				$drivers => implode(', ', $_POST['drivers']),
				':active' => $activasion
			));
			$id = $db->lastInsertId('memberID');
 
$title = "Register";

include ( 'includes/header.php' );
?>
<!--CONTENT-->

        <!-- Page Title -->
		<div class="section section-breadcrumbs">
			<div class="container">
				<div class="row">
					<div class="col-md-12">
						<h1>Register</h1>
					</div>
				</div>
			</div>
		</div>
        
        <div class="section">
	    	<div class="container">
				<div class="row">
					<div class="col-sm-12">
						<div class="basic-login">
							<form role="form" method="post" action="" autocomplete="off">
				<h2>Please Sign Up</h2>
				<p>Already a member? <a href='login.php'>Login</a></p>
				<hr>

				<?php
				//check for any errors
				if(isset($error)){
					foreach($error as $error){
						echo '<p class="bg-danger">'.$error.'</p>';
					}
				}

				//if action is joined show sucess
				if(isset($_GET['action']) && $_GET['action'] == 'joined'){
					echo "<h2 class='bg-success'>Registration successful, please check your email to activate your account.</h2>";
				}
				?>

				<div class="form-group">
					<input type="text" name="username" id="username" class="form-control input-lg" placeholder="User Name" value="<?php if(isset($error)){ echo $_POST['username']; } ?>" tabindex="1">
				</div>
				<div class="form-group">
					<input type="email" name="email" id="email" class="form-control input-lg" placeholder="Email Address" value="<?php if(isset($error)){ echo $_POST['email']; } ?>" tabindex="2">
				</div>
				<div class="row">
					<div class="col-xs-6 col-sm-6 col-md-6">
						<div class="form-group">
							<input type="password" name="password" id="password" class="form-control input-lg" placeholder="Password" tabindex="3">
						</div>
					</div>
					<div class="col-xs-6 col-sm-6 col-md-6">
						<div class="form-group">
							<input type="password" name="passwordConfirm" id="passwordConfirm" class="form-control input-lg" placeholder="Confirm Password" tabindex="4">
						</div>
					</div>
                    
                    <div class="col-xs-6 col-sm-6 col-md-6">
						<div class="form-group">
						<input type="checkbox" name="drivers[]" value="jasonplato"> Jason Plato
                        <br>
                        <input type="checkbox" name="drivers[]" value="ashsutton"> Ash Sutton
                        <br>
                        <input type="checkbox" name="drivers[]" value="joshcook"> Josh Cook
                        <br>
						</div>
					</div>
                    
				</div>

				<div class="row">
					<div class="col-xs-6 col-md-6"><input type="submit" name="submit" value="Register" class="btn btn-primary btn-block btn-lg" tabindex="5"></div>
				</div>
			</form>
						</div>
					</div>
				</div>
			</div>
		</div>

	    <?php include( 'includes/footer.php' ); ?>

UPDATE: I think the issue in this section of coding

$stmt->execute(array(
				':username' => $_POST['username'],
				':password' => $hashedpassword,
				':email' => $_POST['email'],	
				$drivers => implode(', ', $_POST['drivers']),
				':active' => $activasion
			));

the error seems to be on line 74 which is below

$drivers => implode(', ', $_POST['drivers']),

Can anyone help please, thank you in advance