CodeIgniter provides a comprehensive data validation class that helps minimize the amount of code you’ll write.


Before explaining CodeIgniter’s approach to data validation, let’s describe the ideal scenario:

  1. A form is displayed.
  2. You fill it in and submit it.
  3. If you submitted something invalid, or perhaps missed a required item, the form is redisplayed containing your data along with an error message describing the problem.
  4. This process continues until you have submitted a valid form.

On the receiving end, the script must:

  1. Check for required data.
  2. Verify that the data is of the correct type, and meets the correct criteria. For example, if a username is submitted it must be validated to contain only permitted characters. It must be of a minimum length, and not exceed a maximum length. The username can’t be someone else’s existing username, or perhaps even a reserved word. Etc.
  3. Sanitize the data for security.
  4. Pre-format the data if needed (Does the data need to be trimmed? HTML encoded? Etc.)
  5. Prep the data for insertion in the database.

Although there is nothing terribly complex about the above process, it usually requires a significant amount of code, and to display error messages, various control structures are usually placed within the form HTML. Form validation, while simple to create, is generally very messy and tedious to implement.

Form Validation Tutorial

What follows is a “hands on” tutorial for implementing CodeIgniter’s Form Validation.

In order to implement form validation you’ll need three things:

  1. A View file containing a form.
  2. A View file containing a “success” message to be displayed upon successful submission.
  3. A controller method to receive and process the submitted data.

Let’s create those three things, using a member sign-up form as the example.

The Form

Using a text editor, create a form called Signup.php. In it, place this code and save it to your application/Views/ folder:

    <title>My Form</title>

<?= $validation->listErrors() ?>

<?= form_open('form') ?>

<input type="text" name="username" value="" size="50" />

<input type="text" name="password" value="" size="50" />

<h5>Password Confirm</h5>
<input type="text" name="passconf" value="" size="50" />

<h5>Email Address</h5>
<input type="text" name="email" value="" size="50" />

<div><input type="submit" value="Submit" /></div>



The Success Page

Using a text editor, create a form called Success.php. In it, place this code and save it to your application/Views/ folder:

    <title>My Form</title>

<h3>Your form was successfully submitted!</h3>

<p><?= anchor('form', 'Try it again!') ?></p>


The Controller

Using a text editor, create a controller called Form.php. In it, place this code and save it to your application/Controllers/ folder:

<?php namespace App\Controllers;

use CodeIgniter\Controller;

class Form extends Controller
        public function index()
                helper(['form', 'url']);

                if (! $this->validate([]))
                        echo view('Signup', [
                                'validation' => $this->validation
                        echo view('Success');

Try it!

To try your form, visit your site using a URL similar to this one:

If you submit the form you should simply see the form reload. That’s because you haven’t set up any validation rules yet.

Since you haven’t told the Validation class to validate anything yet, it returns false (boolean false) by default. The ``validate()`` method only returns true if it has successfully applied your rules without any of them failing.


You’ll notice several things about the above pages:

The form (Signup.php) is a standard web form with a couple exceptions:

  1. It uses a form helper to create the form opening. Technically, this isn’t necessary. You could create the form using standard HTML. However, the benefit of using the helper is that it generates the action URL for you, based on the URL in your config file. This makes your application more portable in the event your URLs change.

  2. At the top of the form you’ll notice the following function call:

    <?= $validation->listErrors() ?>

    This function will return any error messages sent back by the validator. If there are no messages it returns an empty string.

The controller (Form.php) has one method: index(). This method uses the Controller-provided validate method and loads the form helper and URL helper used by your view files. It also runs the validation routine. Based on whether the validation was successful it either presents the form or the success page.

Loading the Library

The library is loaded as a service named validation:

$validation =  \Config\Services::validation();

This automatically loads the Config\Validation file which contains settings for including multiple Rule sets, and collections of rules that can be easily reused.


You may never need to use this method, as both the Controller and the Model provide methods to make validation even easier.

Setting Validation Rules

CodeIgniter lets you set as many validation rules as you need for a given field, cascading them in order. To set validation rules you will use the setRule(), setRules(), or withRequest() methods.


This method sets a single rule. It takes the name of field as the first parameter, and a string with a pipe-delimited list of rules that should be applied:

$validation->setRule('username', 'required');

The field name must match the key of any data array that is sent in. If the data is taken directly from $_POST, then it must be an exact match for the form input name.


Like, setRule(), but accepts an array of field names and their rules:

    'username' => 'required',
    'password' => 'required|min_length[10]'


One of the most common times you will use the validation library is when validating data that was input from an HTML form. If desired, you can pass an instance of the current Request object and it will take all of the $_POST data and set it as the data to be validated:


Validate 1 Value

Validate one value against a rule.

$validation->check($value, ‘required’);

Saving Sets of Validation Rules to the Config File

A nice feature of the Validation class is that it permits you to store all your validation rules for your entire application in a config file. You organize the rules into “groups”. You can specify a different group every time you run the validation.

How to save your rules

To store your validation rules, simply create a new public property in the Config\Validation class with the name of your group. This element will hold an array with your validation rules. As shown earlier, the validation array will have this prototype:

class Validation
    public $signup = [
        'username'     => 'required',
        'password'     => 'required',
        'pass_confirm' => 'required|matches[password]',
        'email'        => 'required|valid_email'

You can specify the group to use when you call the run() method:

$validation->run($data, $signup);

You can also store custom error messages in this configuration file by naming the property the same as the group, and appended with _errors. These will automatically be used for any errors when this group is used:

class Validation
    public $signup = [
        'username'     => 'required',
        'password'     => 'required',
        'pass_confirm' => 'required|matches[password]',
        'email'        => 'required|valid_email'

    public $signup_errors = [
        'username' => [
            'required'    => 'You must choose a username.',
        'email'    => [
            'valid_email' => 'Please check the Email field. It does not appear to be valid.'

See below for details on the formatting of the array.

Getting & Setting Rule Groups

Get Rule Group

This method gets a rule group from the validation configuration.


Set Rule Group

This method sets a rule group from the validation configuration to the validation service.


Working With Errors

The Validation library provides several methods to help you set error messages, provide custom error messages, and retrieve one or more errors to display.

By default, error messages are derived from language strings in system/Language/en/Validation.php, where each rule has an entry.

TODO: Determine how to easily add custom rule messages.

Setting Custom Error Messages

Both the setRule() and setRules() methods can accept an array of custom messages that will be used as errors specific to each field as their last parameter. This allows for a very pleasant experience for the user since the errors are tailored to each instance. If not custom error message is provided, the default value will be used.

The array is structured as follows:

    'field' => [
        'rule' => 'message',
        'rule' => 'message',

Here is a more practical example:

$rules = [
    'username' => [
        'required'   => 'All accounts must have usernames provided',
    'password' => [
        'min_length' => 'Your password is too short. You want to get hacked?'

        'username' => 'required|is_unique[users.username]',
        'password' => 'required|min_length[10]'

Getting All Errors

If you need to retrieve all error messages for failed fields, you can use the getErrors() method:

$errors = $validation->getErrors();

// Returns:
    'field1' => 'error message',
    'field2' => 'error message',

If no errors exist, an empty array will be returned.

Getting a Single Error

You can retrieve the error for a single field with the getError() method. The only parameter is the field name:

$error = $validation->getError('username');

If no error exists, an empty string will be returned.

Check If Error Exists

You can check to see if an error exists with the hasError() method. The only parameter is the field name:

if ($validation->hasError('username')
    echo $validation->getError('username');

Customizing Error Display

When you call $validation->listErrors() or $validation->showError(), it loads a view file in the background that determines how the errors are displayed. By default, they display in a manner compatible with the Bootstrap CSS framework. You can easily create new views and use them throughout your application.

Creating the Views

The first step is to create the custom views. These can be placed anywhere that the view() method can locate them, which means the standard View directory, or any namespaced View folder will work. For example, you could create a new view at /application/Views/_errors_list.php:

<div class="alert alert-danger" role="alert">
    <?php foreach ($errors as $error) : ?>
        <li><?= esc($error) ?></li>
    <?php endforeach ?>

An array named $errors is available within the view that contains a list of the errors, where the key is the name of the field that had the error, and the value is the error message, like this:

$errors = [
    'username' => 'The username field must be unique.',
    'email'    => 'You must provide a valid email address.'

There are actually two types of views that you can create. The first has an array of all of the errors, and is what we just looked at. The other type is simpler, and only contains a single variable, $error that contains the error message. This is used with the showError() method where a field must be specified:

<span class="help-block"><?= esc($error) ?></span>


Once you have your views created, you need to let the Validation library know about them. Open Config/Validation.php. Inside, you’ll find the $templates property where you can list as many custom views as you want, and provide an short alias they can be referenced by. If we were to add our example file from above, it would look something like:

public $templates = [
    'list'    => 'CodeIgniter\Validation\Views\list',
    'single'  => 'CodeIgniter\Validation\Views\single',
    'my_list' => '_errors_list'

Specifying the Template

You can specify the template to use by passing it’s alias as the first parameter in listErrors:

<?= $validation->listErrors('my_list') ?>

When showing field-specific errors, you can pass the alias as the second parameter to the showError method, right after the name of the field the error should belong to:

<?= $validation->showError('username', 'my_single') ?>

Creating Custom Rules

Rules are stored within simple, namespaced classes. They can be stored any location you would like, as long as the autoloader can find it. These files are called RuleSets. To add a new RuleSet, edit Config/Validation.php and add the new file to the $ruleSets array:

public $ruleSets = [

You can add it as either a simple string with the fully qualified class name, or using the ::class suffix as shown above. The primary benefit here is that it provides some extra navigation capabilities in more advanced IDEs.

Within the file itself, each method is a rule and must accept a string as the first parameter, and must return a boolean true or false value signifying true if it passed the test or false if it did not:

class MyRules
    public function even(string $str): bool
        return (int)$str % 2 == 0;

By default, the system will look within CodeIgniter\Language\en\Validation.php for the language strings used within errors. In custom rules you may provide error messages by accepting an $error variable by reference in the second parameter:

public function even(string $str, string &$error = null): bool
    if ((int)$str % 2 != 0)
        $error = lang('myerrors.evenError');
        return false;

    return true;

Your new custom rule could now be used just like any other rule:

$this->validate($request, [
    'foo' => 'required|even'

Allowing Parameters

If your method needs to work with parameters, the function will need a minimum of three parameters: the string to validate, the parameter string, and an array with all of the data that was submitted the form. The $data array is especially handy for rules like require_with that needs to check the value of another submitted field to base its result on:

public function required_with($str, string $fields, array $data): bool
        $fields = explode(',', $fields);

        // If the field is present we can safely assume that
        // the field is here, no matter whether the corresponding
        // search field is present or not.
        $present = $this->required($data[$str] ?? null);

        if ($present === true)
                return true;

        // Still here? Then we fail this test if
        // any of the fields are present in $data
        $requiredFields = array_intersect($fields, $data);

        $requiredFields = array_filter($requiredFields, function($item)
                return ! empty($item);

        return ! (bool)count($requiredFields);

Custom errors can be returned as the fourth parameter, just as described above.

Available Rules

The following is a list of all the native rules that are available to use:

Rule Parameter Description Example
alpha No Fails if field has anything other than alphabetic characters.  
alpha_space No Fails if field contains anything other than alphabetic characters or spaces.  
alpha_dash No Fails if field contains anything other than alpha-numeric characters, underscores or dashes.  
alpha_numeric No Fails if field contains anything other than alpha-numeric characters or numbers.  
alpha_numeric_space No Fails if field contains anything other than alpha-numeric characters, numbers or space.  
decimal No Fails if field contains anything other than a decimal number.  
differs Yes Fails if field does not differ from the one in the parameter. differs[field_name]
exact_length Yes Fails if field is not exactly the parameter value. exact_length[5]
greater_than Yes Fails if field is less than or equal to the parameter value or not numeric. greater_than[8]
greater_than_equal_to Yes Fails if field is less than the parameter value, or not numeric. greater_than_equal_to[5]
in_list Yes Fails if field is not within a predetermined list. in_list[red,blue,green]
integer No Fails if field contains anything other than an integer.  
is_natural No Fails if field contains anything other than a natural number: 0, 1, 2, 3, etc.  
is_natural_no_zero No Fails if field contains anything other than a natural number, except zero: 1, 2, 3, etc.  
less_than Yes Fails if field is greater than or equal to the parameter value or not numeric. less_than[8]
less_then_equal_to Yes Fails if field is greater than the parameter value or not numeric. less_than_equal_to[8]
matches Yes The value must match the value of the field in the parameter. matches[field]
max_length Yes Fails if field is longer than the parameter value. max_length[8]
min_length Yes Fails if field is shorter than the parameter value. min_length[3]
numeric No Fails if field contains anything other than numeric characters.  
regex_match Yes Fails if field does not match the regular expression. regex_match[/regex/]
required No Fails if the field is empty.  
required_with Yes The field is required if any of the fields in the parameter are set. required_with[field1,field2]
required_without Yes The field is required when any of the fields in the parameter are not set. required_without[field1,field2]
is_unique Yes Checks if this field value exists in the database. Optionally set a column and value to ignore, useful when updating records to ignore itself. is_unique[table.field,ignore_field,ignore_value]
timezone No Fails if field does match a timezone per timezone_identifiers_list  
valid_base64 No Fails if field contains anything other than valid Base64 characters.  
valid_email No Fails if field does not contain a valid email address.  
valid_emails No Fails if any value provided in a comma separated list is not a valid email.  
valid_ip No Fails if the supplied IP is not valid. Accepts an optional parameter of ‘ipv4’ or ‘ipv6’ to specify an IP format. valid_ip[ipv6]
valid_url No Fails if field does not contain a valid URL.  
valid_cc_number Yes Verifies that the credit card number matches the format used by the specified provider. Current supported providers are: American Express (amex), China Unionpay (unionpay), Diners Club CarteBlance (carteblanche), Diners Club (dinersclub), Discover Card (discover), Interpayment (interpayment), JCB (jcb), Maestro (maestro), Dankort (dankort), NSPK MIR (mir), MasterCard (mastercard), Visa (visa), UATP (uatp), Verve (verve), CIBC Convenience Card (cibc), Royal Bank of Canada Client Card (rbc), TD Canada Trust Access Card (tdtrust), Scotiabank Scotia Card (scotia), BMO ABM Card (bmoabm), HSBC Canada Card (hsbc) valid_cc_number[amex]

Rules for File Uploads

These validation rules enable you to do the basic checks you might need to verify that uploaded files meet your business needs. Since the value of a file upload HTML field doesn’t exist, and is stored in the $_FILES global, the name of the input field will need to be used twice. Once to specify the field name as you would for any other rule, but again as the first parameter of all file upload related rules:

// In the HTML
<input type="file" name="avatar">

// In the controller
    'avatar' => 'uploaded[avatar]|max_size[avatar,1024]'
Rule Parameter Description Example
uploaded Yes Fails if the name of the parameter does not match the name of any uploaded files. uploaded[field_name]
max_size Yes Fails if the uploaded file named in the parameter is larger than the second parameter in kilobytes (kb). max_size[field_name,2048]
max_dims Yes Files if the maximum width and height of an uploaded image exceeds values. The first parameter is the field name. The second is the width, and the third is the height. Will also fail if the file cannot be determined to be an image. max_dims[field_name,300,150]
mime_in Yes Fails if the file’s mime type is not one listed in the parameter. mime_in[field_name,image/png,image/jpg]
ext_in Yes Fails if the file’s extension is not one listed in the parameter. ext_in[field_name,png,jpg,gif]
is_image Yes Fails if the file cannot be determined to be an image based on the mime type. is_image[field_name]


You can also use any native PHP functions that permit up to two parameters, where at least one is required (to pass the field data).