php后门木马常用的函数大致上可分为四种类型：

1. 执行系统命令: system, passthru, shell_exec, exec, popen,proc_open

   
   

2. 代码执行与加密: eval, assert, call_user_func,base64_decode, gzinflate,gzuncompress, gzdecode, str_rot13

3. 文件包含与生成: require, require_once, include, include_once,file_get_contents, file_put_contents, fputs, fwrite

4. .htaccess: SetHandler, auto_prepend_file, auto_append_file