Calculate Number of Days Between Two Fields

March 28, 2018

Turn your Gravity Form into a booking calculator!

Use with two date fields (a start date and an end date), as well as a Product, Quantity and Total fields to convert Gravity forms into a booking calendar.

/**
* Gravity Wiz // Calculate Number of Days Between Two Gravity Form Date Fields
*
* Allows you to calculated the number of days between two Gravity Form date fields and populate that number into a
* field on your Gravity Form.
*
* @version   1.1
* @author    David Smith <[email protected]>
* @license   GPL-2.0+
* @link      https://gravitywiz.com/calculate-number-of-days-between-two-dates/
* @copyright 2013 Gravity Wiz
*/
class GWDayCount {
    private static $script_output;
    function __construct( $args ) {
        extract( wp_parse_args( $args, array(
            'form_id'          => false,
            'start_field_id'   => false,
            'end_field_id'     => false,
            'count_field_id'   => false,
            'include_end_date' => true,
            ) ) );
        $this->form_id        = $form_id;
        $this->start_field_id = $start_field_id;
        $this->end_field_id   = $end_field_id;
        $this->count_field_id = $count_field_id;
        $this->count_adjust   = $include_end_date ? 1 : 0;
        add_filter( "gform_pre_render_{$form_id}", array( &$this, 'load_form_script') );
        add_action( "gform_pre_submission_{$form_id}", array( &$this, 'override_submitted_value') );
    }
    function load_form_script( $form ) {
        // workaround to make this work for < 1.7
        $this->form = $form;
        add_filter( 'gform_init_scripts_footer', array( &$this, 'add_init_script' ) );
        if( self::$script_output )
            return $form;
        ?>

        <script type="text/javascript">
        (function($){
            window.gwdc = function( options ) {
                this.options = options;
                this.startDateInput = $( '#input_' + this.options.formId + '_' + this.options.startFieldId );
                this.endDateInput = $( '#input_' + this.options.formId + '_' + this.options.endFieldId );
                this.countInput = $( '#input_' + this.options.formId + '_' + this.options.countFieldId );
                this.init = function() {
                    var gwdc = this;
                    // add data for "format" for parsing date
                    gwdc.startDateInput.data( 'format', this.options.startDateFormat );
                    gwdc.endDateInput.data( 'format', this.options.endDateFormat );
                    gwdc.populateDayCount();
                    gwdc.startDateInput.change( function() {
                        gwdc.populateDayCount();
                    } );
                    gwdc.endDateInput.change( function() {
                        gwdc.populateDayCount();
                    } );
                    $( '#ui-datepicker-div' ).hide();
                }
                this.getDayCount = function() {
                    var startDate = this.parseDate( this.startDateInput.val(), this.startDateInput.data('format') )
                    var endDate = this.parseDate( this.endDateInput.val(), this.endDateInput.data('format') );
                    var dayCount = 0;
                    if( !this.isValidDate( startDate ) || !this.isValidDate( endDate ) )
                        return '';
                    if( startDate > endDate ) {
                        return 0;
                    } else {
                        var diff = endDate - startDate;
                        dayCount = diff / ( 60 * 60 * 24 * 1000 ); // secs * mins * hours * milliseconds
                        dayCount = Math.round( dayCount ) + this.options.countAdjust;
                        return dayCount;
                    }
                }
                this.parseDate = function( value, format ) {
                    if( !value )
                        return false;
                    format = format.split('_');
                    var dateFormat = format[0];
                    var separators = { slash: '/', dash: '-', dot: '.' };
                    var separator = format.length > 1 ? separators[format[1]] : separators.slash;
                    var dateArr = value.split(separator);
                    switch( dateFormat ) {
                    case 'mdy':
                        return new Date( dateArr[2], dateArr[0] - 1, dateArr[1] );
                    case 'dmy':
                        return new Date( dateArr[2], dateArr[1] - 1, dateArr[0] );
                    case 'ymd':
                        return new Date( dateArr[0], dateArr[1] - 1, dateArr[2] );
                    }
                    return false;
                }
                this.populateDayCount = function() {
                    this.countInput.val( this.getDayCount() ).change();
                }
                this.isValidDate = function( date ) {
                    return !isNaN( Date.parse( date ) );
                }
                this.init();
            }
        })(jQuery);
        </script>

        <?php
        self::$script_output = true;
        return $form;
    }
    function add_init_script( $return ) {
        $start_field_format = false;
        $end_field_format = false;
        foreach( $this->form['fields'] as &$field ) {
            if( $field['id'] == $this->start_field_id )
                $start_field_format = $field['dateFormat'] ? $field['dateFormat'] : 'mdy';
            if( $field['id'] == $this->end_field_id )
                $end_field_format = $field['dateFormat'] ? $field['dateFormat'] : 'mdy';
        }
        $script = "new gwdc({
                formId:             {$this->form['id']},
                startFieldId:       {$this->start_field_id},
                startDateFormat:    '$start_field_format',
                endFieldId:         {$this->end_field_id},
                endDateFormat:      '$end_field_format',
                countFieldId:       {$this->count_field_id},
                countAdjust:        {$this->count_adjust}
            });";
        $slug = implode( '_', array( 'gw_display_count', $this->start_field_id, $this->end_field_id, $this->count_field_id ) );
        GFFormDisplay::add_init_script( $this->form['id'], $slug, GFFormDisplay::ON_PAGE_RENDER, $script );
        // remove filter so init script is not output on subsequent forms
        remove_filter( 'gform_init_scripts_footer', array( &$this, 'add_init_script' ) );
        return $return;
    }
    function override_submitted_value( $form ) {
        $start_date = false;
        $end_date = false;
        foreach( $form['fields'] as &$field ) {
            if( $field['id'] == $this->start_field_id )
                $start_date = self::parse_field_date( $field );
            if( $field['id'] == $this->end_field_id )
                $end_date = self::parse_field_date( $field );
        }
        if( $start_date > $end_date ) {
            $day_count = 0;
        } else {
            $diff = $end_date - $start_date;
            $day_count = $diff / ( 60 * 60 * 24 ); // secs * mins * hours
            $day_count = round( $day_count ) + $this->count_adjust;
        }
        $_POST["input_{$this->count_field_id}"] = $day_count;
    }
    static function parse_field_date( $field ) {
        $date_value = rgpost("input_{$field['id']}");
        $date_format = empty( $field['dateFormat'] ) ? 'mdy' : esc_attr( $field['dateFormat'] );
        $date_info = GFCommon::parse_date( $date_value, $date_format );
        if( empty( $date_info ) )
            return false;
        return strtotime( "{$date_info['year']}-{$date_info['month']}-{$date_info['day']}" );
    }
}
# Configuration
new GWDayCount( array(     // Add your Gravity Form information here!
    'form_id'        => 16,
    'start_field_id' => 1,
    'end_field_id'   => 2,
    'count_field_id' => 4
) );

Sourced here.