How to retrieve values from database using php and mysql - php

Question

I am trying to write a script where I need to retrieve email from the database and send a url link to that email,it works, but I want it to be in proper query, since as a beginner I tried but not sure if the queries are correct, I have trouble retrieving the people_id, when the link is sent i am getting the token but not the student_id, how do I fix this issue
<?php
error_reporting(1);
session_start();
include 'includes/db.php';
include 'includes/tokengen.php';
include('classes/phpmailer/phpmailer.php');
if($_POST["Submit"]=="Submit"){
$idcode=$_POST['idcode'];
$_SESSION['idcode'] = $post['idcode'];
$sql = "SELECT * FROM student WHERE idcode = :idcode";
$stmt = $pdo->prepare($sql);
$stmt->bindValue(':idcode', $idcode);
$stmt->execute();
$result = $stmt->fetch(PDO::FETCH_ASSOC);
if(!empty($result)){
$email = $result['email'];
//followed a online resource*Doubt
//echo $email;
$token = generateToken();
//echo $token;
$sql = "UPDATE student SET token = :token WHERE email = :email";
//echo $email;
$stmt = $pdo->prepare($sql);
$stmt->execute(array(
':token' => $token,
':email' => $email
));
$result1 = $stmt->fetch(PDO::FETCH_ASSOC);
if(!empty($result)){
$mail = new PHPMailer;
$mail->isSMTP();
//From email address and name
$mail->From = "graymatter.com";
$mail->FromName = "johndoe";
//To address and name
$mail->addAddress("$email", "janedoe");
//echo $email;
//$mail->addAddress("recepient1#example.com"); //Recipient name is optional
//Address to which recipient will reply
$mail->addReplyTo("", "Reply");
//CC and BCC
//$mail->addCC("cc#example.com");
//$mail->addBCC("bcc#example.com");
//Send HTML or Plain Text email
$mail->isHTML(true);
$mail->Subject = "You Registration Link!";
$mail->Body = "http://www.empty.com/register/registration.php?token=$token&student_id=student_id";
$mail->AltBody = 'Click to Register';
if(!$mail->send())
{
echo "Mailer Error: " . $mail->ErrorInfo;
}
else
{
echo "Message has been sent successfully";
}
}
}
else{
echo 'You are not Registered';
}
}
?>
<div class="container">
<div class="row">
<div class="col-md-5 col-md-offset-3 well">
<form role="form" class="form-horizontal" action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" name="regform">
<fieldset>
<legend>Login</legend>
<div class="form-group">
<div class="col-md-3">
<label for="txt_email" class="control-label">CCODE:</label>
</div>
<div class="col-md-9">
<div class="form-inline">
<div class="form-group">
<input class="form-control" type="text" name="idcode" required placeholder="STUDENT ID" value="<?= isset($_SESSION["idcode"]) ? $_SESSION["idcode"] : ""; ?>"/>
<label for="idcode" generated="true" class="error">
<?= isset($error_hash["idcode"]) ? $error_hash["idcode"] : "" ?>
</label>
</div>
</div>
</div>
</div>
<div class="form-group">
<div class="col-md-12">
<input type="submit" name="Submit" value="Submit" class="btn btn-primary"/>
</div>
</div>
</fieldset>
</form>
</div>
</div>
</div>