unzip_file( string $file, string $to )

Unzips a specified ZIP file to a location on the Filesystem via the ClassicPress Filesystem Abstraction.


Assumes that WP_Filesystem() has already been called and set up. Does not extract a root-level __MACOSX directory, if present.

Attempts to increase the PHP Memory limit to 256M before uncompressing, However, The most memory required shouldn’t be much larger than the Archive itself.



(string) (Required) Full path and filename of zip archive


(string) (Required) Full path on the filesystem to extract archive to


(mixed) WP_Error on failure, True on success


File: wp-admin/includes/file.php

function unzip_file($file, $to) {
	global $wp_filesystem;

	if ( ! $wp_filesystem || !is_object($wp_filesystem) )
		return new WP_Error('fs_unavailable', __('Could not access filesystem.'));

	// Unzip can use a lot of memory, but not this much hopefully.
	wp_raise_memory_limit( 'admin' );

	$needed_dirs = array();
	$to = trailingslashit($to);

	// Determine any parent dir's needed (of the upgrade directory)
	if ( ! $wp_filesystem->is_dir($to) ) { //Only do parents if no children exist
		$path = preg_split('![/\\\]!', untrailingslashit($to));
		for ( $i = count($path); $i >= 0; $i-- ) {
			if ( empty($path[$i]) )

			$dir = implode('/', array_slice($path, 0, $i+1) );
			if ( preg_match('!^[a-z]:$!i', $dir) ) // Skip it if it looks like a Windows Drive letter.

			if ( ! $wp_filesystem->is_dir($dir) )
				$needed_dirs[] = $dir;
				break; // A folder exists, therefor, we dont need the check the levels below this

	 * Filters whether to use ZipArchive to unzip archives.
	 * @since WP-3.0.0
	 * @param bool $ziparchive Whether to use ZipArchive. Default true.
	if ( class_exists( 'ZipArchive', false ) && apply_filters( 'unzip_file_use_ziparchive', true ) ) {
		$result = _unzip_file_ziparchive($file, $to, $needed_dirs);
		if ( true === $result ) {
			return $result;
		} elseif ( is_wp_error($result) ) {
			if ( 'incompatible_archive' != $result->get_error_code() )
				return $result;
	// Fall through to PclZip if ZipArchive is not available, or encountered an error opening the file.
	return _unzip_file_pclzip($file, $to, $needed_dirs);


Version Description
WP-2.5.0 Introduced.