Php – validation max_length, min_length in codeigniter

This is the JavaScript solution:

 <input type="text"
    pattern="[a-zA-Z]+"
    oninvalid="setCustomValidity('Please enter Alphabets.')"
    onchange="try{setCustomValidity('')}catch(e){}" />

The "onchange" event needs when you set an invalid input data, then correct the input and send the form again. I've tested it on Firefox, Chrome and Safari.

But for Modern Browsers:

Modern browsers didn't need any JavaScript for validation. Just do it like this:

<input type="text"
    pattern="[a-zA-Z]+"
    title="Please enter Alphabets."
    required="" />

If you want to permanently over-ride the error message just hard code it into the form_validation_lang.php file.
(Located at system/language/english)

It you want the choice the extend the form_validation class adding your custom required function and add the appropriate error message in the lang file.

For example;

class MY_Form_validation {
    public function custom_required($str) {
        if ( ! is_array($str)) {
            return (trim($str) == '') ? FALSE : TRUE;
        } else {
            return ( ! empty($str));
        }
    }
}

Then in the lang file;

$lang['custom_required'] = "%s can not be blank.";