Gravity Forms: Validate Arrival & Departure Dates

hyphen_gravity_forms_date_validation.php

/***
* Gravity Forms: Validate to ensure date fields are not the same or todays date
*
* This will validate the fields on form submission and return a validation error on the fields in question.
* In this case it validates an Arrival and Departure date against each other and today's date.
*
* Code goes in your theme's functions.php file.
***/

add_filter('gform_field_validation','validate_dates',10,4);
function validate_dates($result,$value,$form,$field){
	
	// Set ut variables for use
	$today = time(); // Use UNIX timestamp for comparison
	$arrivalDate = '';
	$departureDate = '';
	
	// Arrival Date-field. Replace '4' with your field ID
	if($field['id'] === 4) {
		$date = DateTime::createFromFormat('d/m/Y',$value); // Create DateTime based on the value of the field. Replace 'd/m/Y' with the value of your Date-field
		$arrivalDate = intval($date->format('U')); // Get UNIX timestamp based on $date
		
		// Check if $arrivalDate is before or on today's date, if true; fail validation.
		if($arrivalDate <= $today) {
			$result['is_valid'] = false; // Fail validation
			$result['message'] = "Arrival date can't be on or before today's date."; // Your message here
		}
	}
	
	// Departure Date-field. Replace '7' with your field ID
	if($field['id'] === 7 && $value) {
		$date = DateTime::createFromFormat('d/m/Y',$value);
		$departureDate = intval($date->format('U'));
		
		// Check if $departureDate is before or on $arrivalDate OR before or on today's date, if either is true; fail validation.
		if($departureDate <= $arrivalDate || $departureDate <= $today) {
			$result['is_valid'] = false; // Fail validation
			$result['message'] = "Departure date can't be on or before arrival or today's date."; // Your message here
		}
	}
	return $result;
}