This tutorial focuses on how to automate file compression and extraction (zipping and unzipping) using PHP extensions.

The principal characteristics and functionalities described are centered around the PHP ZipArchive class:

1. Benefits of File Compression

Compressing files when transferring them over the internet offers several advantages:

• Reduced Size: The total size of files is significantly lowered.

• Bandwidth Saving: Compression helps save bandwidth.

• Faster Downloads: Users benefit from faster download speeds.

• Automation: Using PHP functions eliminates the tiresome process of manual compression.

2. Core Archive Management (Opening and Flags)

To start, a new ZipArchive instance is created, followed by calling the open($filename, [$flags]) method. Key optional flags determine how the archive is handled:

• ZipArchive::CREATE: Creates a new archive if one does not exist.

• ZipArchive::OVERWRITE: Overwrites existing contents in the specified archive.

• ZipArchive::EXCL: Results in an error if the archive already exists.

• ZipArchive::RDONLY: Allows opening the archive in read-only mode (available since PHP 7.4.3).

• Using combinations (e.g., ZipArchive::OVERWRITE|ZipArchive::CREATE) allows overwriting an existing archive while simultaneously creating a new one if none is found.

3. Adding Files (Compression)

Once the archive is opened, files can be added:

• Individual Files: The addFile($filename, $localname, $start, $length) method adds a file from a given path to the archive. The $localname parameter sets the file's name inside the archive.

• Multiple Files/Directory Matching: The addGlob($pattern, $flags, $options) method is used to archive multiple files (e.g., all .pdf or .png files).

  • The $options parameter (an associative array) controls the directory structure inside the archive.

  • Options include add_path (prefixing the file's local path) and removeallpath (removing everything from the path except the file name, adding it to the archive root).

• After adding files, the close() method is called to save changes and close the archive.

4. Extracting Content

The extractTo($destination, $entries) method is used to extract archive contents:

• It can extract everything inside the archive (if the second parameter is omitted) or specific files.

• When extracting specific files, the proper path of the file inside the archive must be specified.

• The directory and file structure are preserved during the extraction process.

5. Archive Modification and Control

The ZipArchive class provides further control over the archived contents:

• Counting Files: The number of files can be counted using the count() method or the numFiles property.

• Renaming: The renameName($oldname, $newname) function changes a file's name within the archive.

• Deleting: The deleteName() method can delete an individual file or an entire directory from the archive.