Gravity Forms check on unique email and categoryf field.

gravityforms-unique.php

<?php

/**
 * Hooks into the "gform_validation" filter to test whether or not a new lead is a duplicate of another lead
 * based upon their fields.
 * 
 * @param mixed $validation_result
 * 
 * @return mixed $validation_result
 */
function pronamic_gf_unique_email_and_category( $validation_result ) {
	global $wpdb;
	
	$form_id           = 2;
	$email_field_id    = 2;
	$category_field_id = 4;
	
	$email    = filter_input( INPUT_POST, 'input_' . $email_field_id   , FILTER_SANITIZE_STRING );
	$category = filter_input( INPUT_POST, 'input_' . $category_field_id, FILTER_SANITIZE_STRING );
	
	if ( ! $email || ! $category ) {
		$validation_result;
	}
	
	// This query counts the number of matching values between existing leads and the lead that is being submitted.
	$number_leads = $wpdb->get_var( $wpdb->prepare( "
		SELECT
			COUNT( lead.id )
		FROM
			{$wpdb->prefix}rg_lead AS lead
				LEFT JOIN
			{$wpdb->prefix}rg_lead_detail AS detail_email
					ON lead.id = detail_email.lead_id AND detail_email.field_number = %d 
				LEFT JOIN
			{$wpdb->prefix}rg_lead_detail AS detail_category
					ON lead.id = detail_category.lead_id AND detail_category.field_number = %d
		WHERE
			lead.form_id = %d
				AND
			detail_email.value = %s
				AND
			detail_category.value = %s
		;",
		$email_field_id,
		$category_field_id,
		$form_id,
		$email,
		$category
	) );
	
	if ( $number_leads > 0 ) {
		$validation_result['is_valid'] = false;
 
		foreach ( $validation_result['form']['fields'] as $field_key => $field ) {
			if ( $field['id'] === $email_field_id ) {
				$field['failed_validation'] = true;
				$field['validation_message'] = __( 'Met dit e-mailadres is al gestemd in deze categorie.', 'twentythirteen' );
				
				$validation_result['form']['fields'][ $field_key ] = $field;
			}
		}
	}
	
	return $validation_result;
}
 
add_filter( 'gform_validation_2', 'pronamic_gf_unique_email_and_category' );