http://www.symfony-project.org/forum/index.php?t=msg&&th=8290#msg_34080

Here is a simple example for you to follow.

First change into the directory where you are developing your site and do the normal symfony setup required.

For this example I suggest making a new app.

symfony new test

now make a new module for your app

symfony module test validatetest

No you will see in your project directory, a folder called apps. In there are all your settings and also your modules. So go into apps/modules/validatetest

First got into the template dir and create a file called IndexSuccess.php

in that file put the following code;

<?php use_helper('Validation') ?>
// Where should your form submit to? Well back to the  index action in this case
<?php echo form_tag('/test/validatetest', array('method' => 'POST');?>
// Show an input tag
<?php echo input_tag('testinput')?>
// We want to display the error message here if there  is a prob.
<?php echo form_error('testinput');?>
// See the correlation between the two above lines? The  form_error has the same name as your input tag.
// Now display the submit button
<?php echo submit_tag('Hit Me',array('name' => 'testvalidatesubmit');?>

And that is it for your template. Now open your browser and go to http://<YOURSERVER>/test_dev.php/validatetest

You should now see your form. Now pressing submit will do nothing at this stage. You need to set up the action to do something.

So back in the validatetest module directory, open up the actions directory and you will see a file called actions.class.php

Open that up and put the following code inside the very first method usually called executeIndex()

<?php
public function executeIndex()
{
    // If this is a POST request we want to do something.
    if($this->getRequest()->getMethod() == sfRequest::POST)
    {
       // For the purpose here, we will just redirect
       // to main web page as we just want to see validation  working
      $this->redirect('http://www.symfony-project.org/');
    }
   return sfView::SUCCESS;
}
?>

Basically all the above is doing, is processing your request.

Now we need to set up validation. So back into your validatetest directory you will see a validate directory.

Create a file there called index.yml

Validation can be written into your action, but that takes ages and you end up repeating yourself. So to make life easy configure it in yml.

Now in your new yml file enter in the following.

fillin:
  enabled: true

fields:
  testinput
    required:
        msg: You must provide something here for me to be helpfull.

basically this says, enable fillin of the form when it is submitted and there is an error, so the user don't have to type stuff in again except what was incorrect. Next it defines, well the fields it needs to validate, as you can pick and choose what you want validate (Hint: In production never ever trust your user, validate all, even if it just for the length of a string or for html etc). as this is a simple form, its only one field, the testinput one. We want this to be a required field, so we say so, and we enter the message we want to display to the user when they don't fill it in.

And that is validation set up. Now go back to your form, and don't enter anything into the form field and press submit. You should see your error message if I have been correct above.

Validation in symfony is really cool, and can be quite complex, for example you can even have it check form fields against your db so to make sure an email address is not already there. Normally you would have to write this method all by yourself, but this saves you valuable time.

I do suggest that you read the docs and the book more before you get into this. But please, please play a bit more with it as you will find out how it should work much quicker.