经过反复思考，发现 SELinux 正在阻止写入目录.我发现了一个 good说明发生了什么的教程.我可以通过运行以下命令修复它:

After much head-scratching, it transpired that SELinux was preventing the directory from being written to. I found a good tutorial that explains what's going on. I was able to fix it by running this command:

sudo chcon -R -t httpd_sys_rw_content_t tmp