<div class="form-group">
<label class="col-sm-4 control-label" for="user">Username :</label>
<div class="col-sm-6">
<input type="text" name="username" id="username" class="form-control" required onclick="cek(document.getElementById('username'), this);">
</div>
</div>
<script>
function cek(user)
{
<?php
$n = $_GET['username']))
$query = "SELECT username from user where username ='$n'";
$result= mysqli_query($link, $query);
while ($data= mysqli_fetch_array($result,MYSQLI_BOTH))
{
$p= $data['username'];
echo "if (username.value == \"".$p."\")";
echo "{";
echo "username.setCustomValidity('usernamesudah ada')";
echo "} else {";
echo "username.setCustomValidity('')";
echo "}";
}
}
?>
}
</script>
dari code diatas apakah ada yang salah atau kurang ya, mohon pencerahannya,