Compresses the entire Phar archive using Gzip or Bzip2 compression

# Phar::compress

(PHP 5 >= 5.3.0, PHP 7, PHP 8, PECL phar >= 2.0.0)

Phar::compress — Compresses the entire Phar archive using Gzip or Bzip2 compression

### 说明

public function Phar::compress(int `$compression`, ?string `$extension` = `null`): ?Phar

> 注意: 此方法需要 将 php.ini 中的 `phar.readonly` 设为 `0` 以适合 Phar 对象. 否则, 将抛出PharException.

For tar-based and phar-based phar archives, this method compresses the entire archive using gzip compression or bzip2 compression. The resulting file can be processed with the gunzip command/bunzip command, or accessed directly and transparently with the Phar extension.

For Zip-based phar archives, this method fails with an exception. The zlib extension must be enabled to compress with gzip compression, the bzip2 extension must be enabled in order to compress with bzip2 compression. As with all functionality that modifies the contents of a phar, the phar.readonly INI variable must be off in order to succeed.

In addition, this method automatically renames the archive, appending `.gz`, `.bz2` or removing the extension if passed `Phar::NONE` to remove compression. Alternatively, a file extension may be specified with the second parameter.

### 参数

`compression`

  Compression must be one of `Phar::GZ`, `Phar::BZ2` to add compression, or `Phar::NONE` to remove compression.

`extension`

  By default, the extension is `.phar.gz` or `.phar.bz2` for compressing phar archives, and `.phar.tar.gz` or `.phar.tar.bz2` for compressing tar archives. For decompressing, the default file extensions are `.phar` and `.phar.tar`.

### 返回值

Returns a Phar object, or `null` on failure.

### 错误／异常

Throws BadMethodCallException if the phar.readonly INI variable is on, the zlib extension is not available, or the bzip2 extension is not enabled.

### 更新日志

版本 | 说明
--- | ---
8.0.0 | `extension` is now nullable.

### 示例

示例 #1 A Phar::compress() example

    <?php
    $p = new Phar('/path/to/my.phar', 0, 'my.phar');
    $p['myfile.txt'] = 'hi';
    $p['myfile2.txt'] = 'hi';
    $p1 = $p->compress(Phar::GZ); // copies to /path/to/my.phar.gz
    $p2 = $p->compress(Phar::BZ2); // copies to /path/to/my.phar.bz2
    $p3 = $p2->compress(Phar::NONE); // exception: /path/to/my.phar already exists
    ?>

### 参见

- PharFileInfo::getCompressedSize() - Returns the actual size of the file (with compression) inside the Phar archive
- PharFileInfo::isCompressed() - Returns whether the entry is compressed
- PharFileInfo::compress() - Compresses the current Phar entry with either zlib or bzip2 compression
- PharFileInfo::decompress() - Decompresses the current Phar entry within the phar
- PharData::compress() - Compresses the entire tar/zip archive using Gzip or Bzip2 compression
- Phar::canCompress() - Returns whether phar extension supports compression using either zlib or bzip2
- Phar::isCompressed() - Returns Phar::GZ or PHAR::BZ2 if the entire phar archive is compressed (.tar.gz/tar.bz and so on)
- Phar::decompress() - Decompresses the entire Phar archive
- Phar::getSupportedCompression() - Return array of supported compression algorithms
- Phar::compressFiles() - Compresses all files in the current Phar archive
- Phar::decompressFiles() - Decompresses all files in the current Phar archive

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