Posts in the developer's cookbook category describe topics that require technical knowledge. Be warned and use the techniques at your own risk. Unless you are an experienced developer, you are strongly advised to ask a professional for support.
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This is the first entry in a series of articles to help developers customize Contact Form 7.
The first topic is expanding Contact Form 7’s form-tags. As you probably know, form-tags are code in a specific format within square brackets, usually representing form controls like text input fields and submit buttons. Currently, Contact Form 7 supports 30 different types of form-tags by default.
These are examples of typical form-tags:
[text* your-name] [textarea your-message] [submit "Send"]
They look like WordPress shortcodes, but unlike shortcodes, form-tags only work within a Contact Form 7 form area.
You can add your own custom form-tags as well. There are two steps to add custom form-tags: (1) register form-tag types and a corresponding callback function, and (2) define the callback function. Let’s look at each step.
wpcf7_add_form_tag
To register form-tag types, call wpcf7_add_form_tag()
function. wpcf7_add_form_tag()
accepts three parameters (two required and one optional).
The first parameter is a string value containing the type of the tag. The first word in a form-tag is its type. In the examples presented above, “text*”, “textarea”, and “submit” are types. You can use lower-case letters ([a-z]
), digits ([0-9]
), underscores (“_
“), and asterisks (“*
“) in a form-tag type. Tag types with a trailing asterisk (e.g., “text*”, “email*”) are used for required input fields.
If you have two or more form-tag types sharing the same callback function, you may want to register them together. In such cases, specify an array of strings as the first parameter.
The second parameter is a callback function called when Contact Form 7 parses the form-tag. More on callback functions later.
The optional third parameter is an array of features that the form-tag type supports. For example, a form-tag type whose instances have a name part supports name-attr
feature.
The name of a form-tag is the second word in the form-tag. In the examples above, “your-name” and “your-message” are names. Some form-tags don’t have names, like [submit "Send"]
.
For form-tag types supporting name-attr
feature, pass array( 'name-attr' => true )
as the third parameter of wpcf7_add_form_tag()
.
Note that you have to use wpcf7_init
action hook when you call wpcf7_add_form_tag()
. For reference, see how Contact Form 7 registers default form-tags.
add_action( 'wpcf7_init', 'wpcf7_add_form_tag_text' );
function wpcf7_add_form_tag_text() {
wpcf7_add_form_tag(
array( 'text', 'text*', 'email', 'email*', 'url', 'url*', 'tel', 'tel*' ),
'wpcf7_text_form_tag_handler',
array( 'name-attr' => true )
);
}
Callback function
The next step is defining the callback function. This function takes a WPCF7_FormTag
object as its only argument, which represents information from an actual form-tag, including its type, name, options, values, etc.
The callback function must return a text value. Usually they return HTML snippets that represent a form control. The returned text replaces the form-tag when Contact Form 7 generates a form from a form template containing form-tags.
As a demonstration, let’s create a simple form-tag that displays the current time (let’s call it “[clock]”).
Add the following code at an appropriate place. Many developers prefer to use theme’s functions.php file for small custom coding. Don’t directly edit files in the plugin (contact-form-7
) folder because you risk breaking the plugin code, and you’ll lose your customization when the plugin is updated.
add_action( 'wpcf7_init', 'custom_add_form_tag_clock' );
function custom_add_form_tag_clock() {
wpcf7_add_form_tag( 'clock', 'custom_clock_form_tag_handler' ); // "clock" is the type of the form-tag
}
function custom_clock_form_tag_handler( $tag ) {
return date_i18n( get_option( 'time_format' ) );
}
Then, add this line to your form area:
Current Time: [clock]
If it works correctly, you should see a line like this in the form:
Current Time: 12:16 pm
That’s it. Obviously this “[clock]” demo is too simple for practical use, but it’s enough to show the concept of the Contact Form 7 form-tags. To improve and make it suitable for practical use, you’ll need to learn:
- How to retrieve information from form-tag components and construct more complex form controls using this information.
- How to validate user input, and if it’s invalid, how to show a validation error.
Upcoming recipes will cover these areas.