How to make a warning message if possible duplicate entry is added? - php

Question

I have here the code for insertion using PDO and the insertion is working fine my problem is that how can i can determine if i inputted in the textbox the record that is already in the database,in my database ihave a column of ID, Firstname and Lastname, ID is auto increment,Firstname is set to unique and lastly is password set to varchar..what i want to happen is that when try to insert a record that is already in the database i want a warning message or maybe a alert message that tells me that "the record is already duplicate"..can somebody please help me with it?
here is the code
class.php
public function create($username,$password,$province)
{
try
{
$stmt = $this->db->prepare("INSERT INTO login(Firstname,Lastname) VALUES(:Firstname, :Lastname)");
$stmt->bindparam(":Firstname",$Firstname);
$stmt->bindparam(":Lastname",$Lastname);
$stmt->execute();
return true;
}
catch(PDOException $e)
{
echo $e->getMessage();
return false;
}
}
and here is index.php
<?php
include_once 'dbconfig.php';
if(isset($_POST['btn-save']))
{
$username = $_POST['Firstname'];
$password = $_POST['Lastname'];
if($crud->create($Firstname,$Lastname))
{
echo "<script type='text/javascript'>alert('Saved!');</script>";
}
else
{
echo "<script type='text/javascript'>alert('Insertion Failed!'); </script>";
}
}
?>
<form method="POST" class="signin" action="" name="Add" target="iframe">
<fieldset class="textbox">
<label class="username">
<span>Username</span>
<input id="Firstname" name="Firstname" value="" type="text" placeholder="Username" required/>
</label>
<label class="password">
<span>Password</span>
<input id="Lastname" name="Lastname" value="" type="password" Placeholder="Password" required/>
</label>
<br />
<button id="submit" type="submit" name="btn-save">Save</button>
<button id="submit" type="reset" name="reset">Reset</button>
<br />
<br />
<hr>
</fieldset>
</form>

Answer 1

If you have the correct UNIQUE keys set in your database, PDO will already throw such a warning/error. You can easily try it yourself by inserting twice the same name
You should try to change your code to this, as this will throw the actual error. The correct function to call would be PDOStatement::errorInfo
Example code would be like this:
public function create($username,$password,$province)
{
try
{
$stmt = $this->db->prepare("INSERT INTO login(Firstname,Lastname) VALUES(:Firstname, :Lastname)");
$stmt->bindparam(":Firstname",$Firstname);
$stmt->bindparam(":Lastname",$Lastname);
if (!$stmt->execute())
{
throw new Exception('Could not execute SQL statement: ' . var_export($stmt->errorInfo(), TRUE));
}
return true;
}
catch(Exception $e)
{
// Here you can filter on error messages and display a proper one.
return $e->getMessage();
}
}
In your index.php, change your PHP code to this:
if(isset($_POST['btn-save']))
{
$username = $_POST['Firstname'];
$password = $_POST['Lastname'];
$result = $crud->create($Firstname,$Lastname);
if($result === TRUE)
{
echo "<script type='text/javascript'>alert('Saved!');</script>";
}
else
{
echo "<script type='text/javascript'>alert(" . $result . "); </script>";
}
}
An other, better, method would be to do a separate SELECT before you do the actual insert to see if the values you are trying to insert already exist.