Use wp_filesize() instead of filesize() throughout core

src/wp-admin/includes/file.php

@@ -934,7 +934,7 @@ function wp_handle_upload_error( &$file, $message ) {
 		return call_user_func_array( $upload_error_handler, array( &$file, __( 'Specified file failed upload test.' ) ) );
 	}
 
-	$test_file_size = 'wp_handle_upload' === $action ? $file['size'] : filesize( $file['tmp_name'] );
+	$test_file_size = 'wp_handle_upload' === $action ? $file['size'] : wp_filesize( $file['tmp_name'] );
 	// A non-empty file will pass this test.
 	if ( $test_size && ! ( $test_file_size > 0 ) ) {
 		if ( is_multisite() ) {

src/wp-admin/includes/ms.php

@@ -30,7 +30,7 @@ function check_upload_size( $file ) {
 
 	$space_left = get_upload_space_available();
 
-	$file_size = filesize( $file['tmp_name'] );
+	$file_size = wp_filesize( $file['tmp_name'] );
 	if ( $space_left < $file_size ) {
 		/* translators: %s: Required disk space in kilobytes. */
 		$file['error'] = sprintf( __( 'Not enough space to upload. %s KB needed.' ), number_format( ( $file_size - $space_left ) / KB_IN_BYTES ) );

src/wp-admin/includes/plugin.php

@@ -403,7 +403,7 @@ function get_mu_plugins() {
 		$wp_plugins[ $plugin_file ] = $plugin_data;
 	}
 
-	if ( isset( $wp_plugins['index.php'] ) && filesize( WPMU_PLUGIN_DIR . '/index.php' ) <= 30 ) {
+	if ( isset( $wp_plugins['index.php'] ) && wp_filesize( WPMU_PLUGIN_DIR . '/index.php' ) <= 30 ) {
 		// Silence is golden.
 		unset( $wp_plugins['index.php'] );
 	}

src/wp-admin/theme-editor.php

@@ -162,9 +162,9 @@
 $content = '';
 if ( ! empty( $posted_content ) ) {
 	$content = $posted_content;
-} elseif ( ! $error && filesize( $file ) > 0 ) {
+} elseif ( ! $error && wp_filesize( $file ) > 0 ) {
 	$f       = fopen( $file, 'r' );
-	$content = fread( $f, filesize( $file ) );
+	$content = fread( $f, wp_filesize( $file ) );
 
 	if ( str_ends_with( $file, '.php' ) ) {
 		$functions = wp_doc_link_parse( $content );

src/wp-includes/class-wp-customize-manager.php

@@ -6087,7 +6087,7 @@ public function export_header_video_settings( $response, $selective_refresh, $pa
 	public function _validate_header_video( $validity, $value ) {
 		$video = get_attached_file( absint( $value ) );
 		if ( $video ) {
-			$size = filesize( $video );
+			$size = wp_filesize( $video );
 			if ( $size > 8 * MB_IN_BYTES ) {
 				$validity->add(
 					'size_too_large',

src/wp-includes/functions.php

@@ -8881,7 +8881,7 @@ function recurse_dirsize( $directory, $exclude = null, $max_execution_time = nul
 				$path = $directory . '/' . $file;
 				if ( '.' !== $file && '..' !== $file ) {
 					if ( is_file( $path ) ) {
-						$size += filesize( $path );
+						$size += wp_filesize( $path );
 					} elseif ( is_dir( $path ) ) {
 						$handlesize = recurse_dirsize( $path, $exclude, $max_execution_time, $directory_cache );
 						if ( $handlesize > 0 ) {

src/wp-includes/ms-files.php

@@ -49,7 +49,7 @@
 
 header( 'Content-Type: ' . $mimetype ); // Always send this.
 if ( ! str_contains( $_SERVER['SERVER_SOFTWARE'], 'Microsoft-IIS' ) ) {
-	header( 'Content-Length: ' . filesize( $file ) );
+	header( 'Content-Length: ' . wp_filesize( $file ) );
 }
 
 // Optional support for X-Sendfile and X-Accel-Redirect.

src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php

@@ -1581,7 +1581,7 @@ protected function check_upload_size( $file ) {
 
 		$space_left = get_upload_space_available();
 
-		$file_size = filesize( $file['tmp_name'] );
+		$file_size = wp_filesize( $file['tmp_name'] );
 
 		if ( $space_left < $file_size ) {
 			return new WP_Error(

src/wp-includes/rest-api/endpoints/class-wp-rest-edit-site-export-controller.php

@@ -85,7 +85,7 @@ public function export() {
 		$theme_name = basename( get_stylesheet() );
 		header( 'Content-Type: application/zip' );
 		header( 'Content-Disposition: attachment; filename=' . $theme_name . '.zip' );
-		header( 'Content-Length: ' . filesize( $filename ) );
+		header( 'Content-Length: ' . wp_filesize( $filename ) );
 		flush();
 		readfile( $filename );
 		unlink( $filename );