1. 首先安装pear：
curl -o go-pear.php https://pear.php.net/go-pear.phar
看见这个就安装OK：
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 3512k 100 3512k 0 0 392k 0 0:00:08 0:00:08 --:--:-- 732k
2. 然后执行：
会发现在当前目录下会有 go-pear.php
sudo php go-pear.php
输入密码后一直确认就行，这样就安装了pear
3.安装phpDocumentor
到pear的安装目录下，直接执行下面这行命令时，我查了一下我的安装目录在 ./pear/bin/
./pear install phpDocumentor
直接报warning，提示
WARNING: "pear/PhpDocumentor" is deprecated in favor of "channel://pear.phpdoc.org/phpdocumentor"
WARNING: configuration download directory "/tmp/pear/install" is not writeable. Change download_dir config variable to a writeable dir to avoid this warning
WARNING: channel "pear.php.net" has updated its protocols, use "pear channel-update pear.php.net" to update
Cannot install, php_dir for channel "pear.php.net" is not writeable by the current user
好像是channel有问题，查了下资料，作出以下调整
执行
sudo pear channel-discover pear.phpdoc.org
提示成功了
Adding Channel "pear.phpdoc.org" succeeded
Discovery of channel "pear.phpdoc.org" succeeded
4. 然后执行安装phpDocument
sudo pear install phpdoc/phpDocumentor
就可以看到下载成功了