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/**
 * Gravity Perks // GP Unique ID // Prepend Date to Unique ID
 */
add_filter( 'gpui_unique_id', 'add_date_to_unique_id', 10, 3 );
function add_date_to_unique_id( $unique, $form_id, $field_id ) {

	if( $form_id == 1 && $field_id == 2 ) {
		// if $unique was "123", this would change it do something like "01132015_123"
		$unique .= date( 'mdy' ) . '_' . $unique;
	}

	return $unique;
}