在编辑PHP5.6.1时出现了这个错误：
Don't know how to define struct flock on this system, set --enable-opcache=no
解决方法是：
sudo ln -s /usr/local/mysql/lib/libmysqlclient.so /usr/lib/
sudo ln -s /usr/local/mysql/lib/libmysqlclient.so.18 /usr/lib/libmysqlclient.so.18