{
    "require":
    {
        "PHPdocumentor/PHPdocumentor": "*"
    }
}

它是什么,因为我正在尝试使用./composer.phar安装命令将PHPDocumentor安装到一个隔离的文件夹中.但我得到的是

Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - PHPdocumentor/PHPdocumentor v2.0.0 requires PHPdocumentor/template-abstract ~1.2 -> satisfiable by PHPdocumentor/template-abstract[1.2,1.2.1].
    - PHPdocumentor/PHPdocumentor v2.0.1 requires PHPdocumentor/template-abstract ~1.2 -> satisfiable by PHPdocumentor/template-abstract[1.2,1.2.1].
    - PHPdocumentor/PHPdocumentor v2.1.0 requires PHPdocumentor/template-abstract ~1.2 -> satisfiable by PHPdocumentor/template-abstract[1.2,1.2.1].
    - PHPdocumentor/PHPdocumentor v2.2.0 requires PHPdocumentor/template-abstract ~1.2 -> satisfiable by PHPdocumentor/template-abstract[1.2,1.2.1].
    - PHPdocumentor/PHPdocumentor v2.3.2 requires PHPdocumentor/template-abstract ~1.2 -> satisfiable by PHPdocumentor/template-abstract[1.2,1.2.1].
    - PHPdocumentor/PHPdocumentor v2.4.0 requires PHPdocumentor/template-abstract ~1.2 -> satisfiable by PHPdocumentor/template-abstract[1.2,1.2.1].
    - PHPdocumentor/PHPdocumentor v2.3.1 requires dompdf/dompdf dev-master@dev -> no matching package found.
    - PHPdocumentor/PHPdocumentor v2.3.0 requires dompdf/dompdf dev-master@dev -> no matching package found.
    - PHPdocumentor/template-abstract 1.2.1 requires ext-xsl * -> the requested PHP extension xsl is missing from your system.
    - PHPdocumentor/template-abstract 1.2 requires ext-xsl * -> the requested PHP extension xsl is missing from your system.
    - Installation request for PHPdocumentor/PHPdocumentor * -> satisfiable by PHPdocumentor/PHPdocumentor[v2.0.0,v2.0.1,v2.1.0,v2.2.0,v2.3.0,v2.3.1,v2.3.2,v2.4.0].

Potential causes:
 - A typo in the package name
 - The package is not available in a stable-enough version according to your minimum-stability setting
   see <https://groups.google.com/d/topic/composer-dev/_g3ASeIFlrc/discussion> for more details.