How to make fields required programatically in Contact Form 7

In this guide, you will learn how to create custom validation in CF7. This guide is also the solution for programmatically making fields required.

Contact Form 7 uses the validation server-side, which means we need to hook into the PHP functions/filters in order to create custom validations.

In my scenario, I have a select field called type-of-enquiry with 2 options, Sales and Support.

If sales is selected, I am showing and validating country(select) and state(select), if support is selected, I am showing product(select), telephone(tel) and subject(text).

We start off by creating a custom file in our theme or child theme, I’ve named mine “cf7-custom-validation.php” and saved it in a custom folder called “inc” and we import it in our functions.php file using:

functions.php

require_once( get_template_directory() . '/inc/cf7-custom-validation.php' );

cf7-custom-validation.php

<?php
// Block direct access to the file
defined( 'ABSPATH' ) || exit;

/**
 * Each field type has its own validation filter,
 * so we create a function for each type
 */
add_filter( 'wpcf7_validate_select', 'wpharvest_custom_validation_select', 20, 2 );
add_filter( 'wpcf7_validate_tel', 'wpharvest_custom_validation_tel', 20, 2 );
add_filter( 'wpcf7_validate_text', 'wpharvest_custom_validation_text', 20, 2 );

/**
 * Go through all the select fields
 */
function wpharvest_custom_validation_select( $result, $tag ) {

	// Get the type of enquiry from the dropdown
    $enquiryType = isset( $_POST['type-of-enquiry'] ) ? trim( $_POST['type-of-enquiry'] ) : '';

    // If selection is Sales
    if( $enquiryType == 'Sales' ){

    	// If current validation is your-country and is empty then invalidate field
    	if ( 'your-country' == $tag->name && empty( $_POST['your-country'] ) ) {
    		$result->invalidate($tag, "This field is required.");
    	}

    	// We can also make validation dependent on other fields
    	// If current validation is state, the country selected is United States and is empty then invalidate field
    	if ( 'state' == $tag->name && trim( $_POST['your-country'] ) == 'United States' && empty( $_POST['state'] ) ) {
    		$result->invalidate($tag, "This field is required.");
    	}
    }

    // If selection is Support
    if( $enquiryType == 'Support' ){

    	// If current validation is product and is empty then invalidate field
    	if ( 'product' == $tag->name && empty( $_POST['product'] ) ) {
    		$result->invalidate($tag, "This field is required.");
    	}
    }

    return $result;
}

/**
 * Go through all the tel fields
 */
function wpharvest_custom_validation_tel( $result, $tag ) {

	// Get the type of enquiry from the dropdown
    $enquiryType = isset( $_POST['type-of-enquiry'] ) ? trim( $_POST['type-of-enquiry'] ) : '';

    // If selection is Support
    if( $enquiryType == 'Support' ){

    	// If current validation is telephone and is empty then invalidate field
    	if ( 'telephone' == $tag->name && empty( $_POST['telephone'] ) ) {
    		$result->invalidate($tag, "This field is required.");
    	}
    }

    return $result;
}

/**
 * Go through all the text fields
 */
function wpharvest_custom_validation_text( $result, $tag ) {

	// Get the type of enquiry from the dropdown
    $enquiryType = isset( $_POST['type-of-enquiry'] ) ? trim( $_POST['type-of-enquiry'] ) : '';

    // If selection is Support
    if( $enquiryType == 'Support' ){

    	// If current validation is subject and is empty then invalidate field
    	if ( 'subject' == $tag->name && empty( $_POST['subject'] ) ) {
    		$result->invalidate($tag, "This field is required.");
    	}
    }

    return $result;
}