Why is my CodeIgniter 4 custom validation rule not working in form validation?

Question

I'm working on a CodeIgniter 4 project and trying to use a custom validation rule for my form. However, the rule doesn't seem to trigger, and I get no validation errors, even when the input should fail.

Here’s the relevant code:

Custom Rule (App\Validation\CustomRules.php):

namespace App\Validation; class CustomRules { public function noSpecialChars(string $str, string $fields, array $data): bool { return preg_match('/^[a-zA-Z0-9 ]+$/', $str) === 1; } }

Validation Configuration (app/Config/Validation.php):

public $ruleSets = [ \CodeIgniter\Validation\Rules::class, \App\Validation\CustomRules::class, ];

Controller Method:

public function submit() { $validation = \Config\Services::validation(); $rules = [ 'username' => 'required|noSpecialChars' ]; if (!$this->validate($rules)) { return redirect()->back()->withInput()->with('errors', $this->validator->getErrors()); } // proceed with saving }

Even when I input something like John@Doe, it still passes validation. What am I missing here?

If I set up a CI4 project with the code from your post, it gives me a TypeError for the validation rule "Argument 2 passed to App\Validation\CustomRules::noSpecialChars() must be of the type string, null given" because you're not passing any parameters to the function in 'required|noSpecialChars'. So I'm not sure if this'll solve your problem, but your function signature should look like this: public function noSpecialChars(string $str): bool — Marleen
– Marleen, Commented Jun 26 at 8:09

Simon Weber · Accepted Answer · 2025-07-03 08:13:55Z

@Marleen is correct. You have too many parameters in your noSpecialChars function. I have a similar function in my CI4 app that looks like this:

public function alpha_numeric_punct_german(string $str, ?string &$error = null) { // M = Math_Symbol, P = Punctuation, L = Latin if ((bool) preg_match('/^[^\p{M}\p{P}\p{L}\p{N} €]+$/u', $str)) { $error = 'Contains illegal characters'; return false; } return true; }

The $errorargument is optional. You only have to pass string $fields and array $data if you want to pass additional data to your validation rule like for example in in_list[2,5] or valid_date[d.m.Y].

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