Zip a directory via PHP with limited memory usage.

archive.php

<?php
/**
 * Configuration
 */
$filename = 'compressed.zip';
$path = '/path/to/store';

// special case for ALL-INKL
// $path = preg_replace( '/(\/www\/htdocs\/\w+\/).*/', '$1', realpath( __FILE__ ) ) . 'subdir';

/**
 * Configuration end
 */

@ini_set( 'max_execution_time', 30000 );
@ini_set( 'memory_limit', '256M' );

zip_files( $path, './' . $filename );

function zip_files( $source, $destination ) {
	$zip = new ZipArchive();
	if ( $zip->open( $destination, ZIPARCHIVE::CREATE ) === true ) {
		$source = realpath( $source );

		if ( is_dir( $source ) ) {
			$iterator = new RecursiveDirectoryIterator( $source );
			$iterator->setFlags( RecursiveDirectoryIterator::SKIP_DOTS );
			$files = new RecursiveIteratorIterator( $iterator, RecursiveIteratorIterator::SELF_FIRST );

			foreach ( $files as $file ) {
				$file = realpath( $file );

				if ( is_dir( $file ) ) {
					$zip->addEmptyDir( str_replace( $source . DIRECTORY_SEPARATOR, '', $file . DIRECTORY_SEPARATOR ) );
				}
				else if ( is_file( $file ) ) {
					$zip->addFile( $file, str_replace( $source . DIRECTORY_SEPARATOR, '', $file ) );
				}
			}
		}
		else if ( is_file( $source ) ) {
			$zip->addFile( $source, basename( $source ) );
		}
	}

	return $zip->close();
}