Login change in to signup - forms

Question

I have created a HTML5 registration form,is it possible for it to check the email address(inserted first) if it's already used to ask only for password(login) and if it's not to insert other fields needed for signup? using php,js or others.

Answer 1

<form id="signin_student" class="form-signin" method="post">
<h3 class="form-signin-heading"><i class="icon-lock"></i> Register </h3>
<input type="text" class="input-block-level" id="username" name="username" placeholder="NISN" required>
<input type="text" class="input-block-level" id="firstname" name="firstname" placeholder="Nama Depan" required>
<input type="text" class="input-block-level" id="lastname" name="lastname" placeholder="Nama Belakang" required>
<label>Kelas</label>
<select name="class_id" class="input-block-level span5">
<option>Pilih Kelas</option>
<?php
$query = mysql_query("select * from class order by class_name ")or die(mysql_error());
while($row = mysql_fetch_array($query)){
?>
<option value="<?php echo $row['class_id']; ?>"><?php echo $row['class_name']; ?></option>
<?php
}
?>
</select>
<input type="password" class="input-block-level" id="password" name="password" placeholder="Password" required>
<input type="password" class="input-block-level" id="cpassword" name="cpassword" placeholder="Tulis Ulang Password" required>
<button title="Klik untuk Daftar" id="signin" name="login" class="btn btn-info" type="submit"><i class="icon-check icon-large"></i> Daftar</button>
</form>
<script>
jQuery(document).ready(function(){
jQuery("#signin_student").submit(function(e){
e.preventDefault();
var password = jQuery('#password').val();
var cpassword = jQuery('#cpassword').val();
if (password == cpassword){
var formData = jQuery(this).serialize();
$.ajax({
type: "POST",
url: "student_signup.php",
data: formData,
success: function(html){
if(html=='true')
{
var delay = 2000;
setTimeout(function(){ window.location = 'siswa/index.php' }, delay);
}else if(html=='false'){
{ header: 'Data in DB is Not Found' });
}
}
});
}else
{
$.jGrowl("student does not found in the database", { header: 'Sign Up Failed' });
}
});
});
</script>
and file signup.php
<?php
mysql_select_db('db',mysql_connect('localhost','root',''))or die(mysql_error());
session_start();
$username = $_POST['username'];
$password = $_POST['password'];
$firstname = $_POST['firstname'];
$lastname = $_POST['lastname'];
$class_id = $_POST['class_id'];
$query = mysql_query("select * from student where username='$username' and firstname='$firstname' and lastname='$lastname' and class_id = '$class_id'")or die(mysql_error());
$row = mysql_fetch_array($query);
$id = $row['student_id'];
$count = mysql_num_rows($query);
if ($count > 0){
mysql_query("update student set password = '$password', status = 'Registered' where student_id = '$id'")or die(mysql_error());
$_SESSION['id']=$id;
echo 'true';
}else{
echo 'false';
}
?>

Answer 2

Firstly, you could use this code to check when the user stops typing:
Run javascript function when user finishes typing instead of on key up?
Once that is finished, this SQL code may work to check if the email already exists:
SELECT EXISTS(SELECT email FROM email_table)
Then you can simply use a conditional statement to print whether the email exists.