Format Date Merge Tags

<?php
/**
 * Gravity Wiz // Gravity Forms // Format Date Merge Tags
 * https://gravitywiz.com/gravity-forms-date-merge-tags/
 *
 * Adds merge tag modifiers for formatting date merge tags using PHP Date Formats.
 *
 * Plugin Name:  Gravity Forms — Format Date Merge Tags
 * Plugin URI:   https://gravitywiz.com/gravity-forms-date-merge-tags/
 * Description:  Adds merge tag modifiers for formatting date merge tags using PHP Date Formats.
 * Author:       Gravity Wiz
 * Version:      0.4
 * Author URI:   https://gravitywiz.com
 */
add_filter( 'gform_pre_replace_merge_tags', function( $text, $form, $entry, $url_encode, $esc_html, $nl2br, $format ) {

	preg_match_all( '/{[^{]*?:(\d+(\.\d+)?)(:(.*?))?}/mi', $text, $matches, PREG_SET_ORDER );

	foreach ( $matches as $match ) {

		$input_id = $match[1];
		$field    = GFFormsModel::get_field( $form, $input_id );

		if ( ! $field || $field->get_input_type() !== 'date' ) {
			continue;
		}

		$i        = $match[0][0] === '{' ? 4 : 5;
		$modifier = rgar( array_map( 'trim', explode( ',', rgar( $match, $i ) ) ), 0 );
		if ( ! $modifier ) {
			continue;
		}

		$value = GFFormsModel::get_lead_field_value( $entry, $field );
		$value = $field->get_value_merge_tag( $value, $input_id, $entry, $form, $modifier, $value, $url_encode, $esc_html, $format, $nl2br );
		if ( ! $value ) {
			continue;
		}

		$format      = $field->dateFormat ? $field->dateFormat : 'mdy';
		$parsed_date = GFCommon::parse_date( $value, $format );

		// On the Notifications/Confirmation side, & gets encoded to &amp;. Decode it back.
		$modifier = htmlspecialchars_decode( $modifier );

		// For whatever reason, Populate Anything's LMTs works better with `&comma` than `&#44;`. But... date() doesn't
		// like it so let's replace it before we pass it to date().
		$modifier = str_replace( '&comma;', ',', $modifier );

		// phpcs:ignore WordPress.DateTime.RestrictedFunctions.date_date
		$replace = date( $modifier, strtotime( sprintf( '%d-%d-%d', $parsed_date['year'], $parsed_date['month'], $parsed_date['day'] ) ) );

		$text = str_replace( $match[0], $replace, $text );

	}

	return $text;
}, 10, 7 );