Validation

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Overview

The Meta Box plugin has built-in validation module for all fields. You can use validation to make a field required, check password length, check phone number format, etc.

The validation module is built with the popular jQuery validation plugin which makes client side form validation easy, whilst still offering plenty of customization options. The plugin comes bundled with a useful set of validation methods and an API to write your own methods. All bundled methods come with default error messages in English and translations into 37 other languages.

Validation rules

To start using validation in Meta Box, you need to add a key validation to the meta box settings. This key has a parameter rules for validation rules and messages for error messages.

Let’s look at the example:

'validation' => array(
    'rules'  => array(
        'field_id' => array(
            'required'  => true,
            'minlength' => 7,
            // More rules here
        ),
        // Rules for other fields
    ),
)

This example add validation for field_id field. There are 2 validation rules for this field: field is required and minimum length is 7.

So, basically the format for rules is:

'rules' => array(
    'field_id_1' => array(
         // rules for field_id_1
    ),
    'field_id_2' => array(
         // rules for field_id_2
    ),
    // Rules for other fields
),

Built-in validation rules

These are list of basic validation rules that you can use for your fields:

Name	Description
required	Makes the element required.
minlength	Makes the element require a given minimum length.
maxlength	Makes the element require a given maxmimum length.
rangelength	Makes the element require a given value range. Array.
min	Makes the element require a given minimum.
max	Makes the element require a given maximum.
range	Makes the element require a given value range. Array.
email	Makes the element require a valid email
url	Makes the element require a valid url
date	Makes the element require a date.
dateISO	Makes the element require an ISO date.
number	Makes the element require a decimal number.
digits	Makes the element require digits only.
creditcard	Makes the element require a credit card number.
equalTo	Requires the element to be the same as another one. Value must be the ID of another field.
remote	Requests a resource to check the element for validity. Value can be URL of the resource to request for server side validation (string) or options to fully customize the request, see jQuery.ajax. The server side resource is called via jQuery.ajax and gets a key/value pair corresponding to the name of the validated element and its value as a GET parameter. The response is evaluated as JSON and must be true for valid elements, and can be any false, undefined or null for invalid elements, using the default message; or a string, eg. “That name is already taken, try peter123 instead” to display as the error message.

For more details about validation rules, please read the jQuery validation documentation.

Error messages

To use custom error messages, you can add another parameter messages for validation key. This parameter has the same format as rules, but it just contains error messages for each rule.

Look at the example below:

'validation' => array(
    'rules'  => array(
        'field_id' => array(
            'required'  => true,
            'minlength' => 7,
        ),
    ),
    // Optional override of default error messages
    'messages' => array(
        'field_id' => array(
            'required'  => 'Password is required',
            'minlength' => 'Password must be at least 7 characters',
        ),
    )
)

Notes

Gutenberg

The validation hasn’t worked for the block editor (Gutenberg) yet. This is a technical issue that we have with Gutenberg and is a known issue. We’re trying to fix that.

Input name

The jQuery validation library actually uses input name, not input ID. In most cases, field ID is the same as field name. But for some cases such as field is a checkbox list or is a taxonomy with field_type is checkbox_list, e.g. where field has multiple inputs, then all those inputs don’t have IDs.

In this case, you need to use input name for the rules. For example, if you use a taxonomy field with field_type is checkbox_list, you should set validation rules as follows:

'validation' => array(
    'rules'  => array(
        'my_taxonomy[]' => array(
            'required'  => true,
        ),
    ),
    'messages' => array(
        'my_taxonomy[]' => array(
            'required'  => 'You must select a tag to proceed',
        ),
    ),
),

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