Add utf8 with bom csv export option

classes/helpers/FrmCSVExportHelper.php

@@ -90,8 +90,34 @@ class FrmCSVExportHelper {
 	 */
 	protected static $meta = array();
 
+	/**
+	 * Whether to include the BOM (Byte Order Mark) in the CSV file.
+	 * Only applicable for UTF-8 exports.
+	 *
+	 * @since x.x
+	 *
+	 * @var bool
+	 */
+	private static $include_bom = false;
+
+	/**
+	 * Get all options for the CSV export format dropdown.
+	 *
+	 * @since x.x The UTF-8 with BOM option was added.
+	 *
+	 * @return array
+	 */
 	public static function csv_format_options() {
 		$formats = array( 'UTF-8', 'ISO-8859-1', 'windows-1256', 'windows-1251', 'macintosh' );
+
+		// Do not add the UTF-8 with BOM option if this function is called on Global Settings.
+		// This is to improve compatibility with the Export View as CSV add-on (v1.10).
+		// Otherwise, the option will appear twice since it is added in the add-on as well.
+		$on_global_settings_page = 'formidable-settings' === FrmAppHelper::get_param( 'page' );
+		if ( ! $on_global_settings_page ) {
+			array_splice( $formats, 1, 0, 'UTF-8 with BOM' );
+		}
+
 		$formats = apply_filters( 'frm_csv_format_options', $formats );
 
 		return $formats;
@@ -241,6 +267,10 @@ private static function print_file_headers( $filename ) {
 		header( 'Cache-Control: no-cache, must-revalidate' );
 		header( 'Pragma: no-cache' );
 
+		if ( self::$include_bom ) {
+			echo esc_html( chr( 239 ) . chr( 187 ) . chr( 191 ) );
+		}
+
 		do_action(
 			'frm_csv_headers',
 			array(
@@ -250,8 +280,19 @@ private static function print_file_headers( $filename ) {
 		);
 	}
 
+	/**
+	 * Check the POST request data for the CSV format to use.
+	 *
+	 * @return void
+	 */
 	public static function get_csv_format() {
-		$csv_format        = FrmAppHelper::get_post_param( 'csv_format', 'UTF-8', 'sanitize_text_field' );
+		$csv_format = FrmAppHelper::get_post_param( 'csv_format', 'UTF-8', 'sanitize_text_field' );
+
+		if ( 'UTF-8 with BOM' === $csv_format ) {
+			self::$include_bom = true;
+			$csv_format        = 'UTF-8';
+		}
+
 		$csv_format        = apply_filters( 'frm_csv_format', $csv_format, self::get_standard_filter_args() );
 		self::$to_encoding = $csv_format;
 	}