You create your own php.ini in your web folder. You don't have to have all the value in php.ini, just something you want to rewrite. For example, your php.ini can only have one line like this
disable_functions = exec,execl,system,passthru,shell_exec,set_time_limit,escapeshellarg,escapeshellcmd,proc_close,ini_alter,proc_open,dl,popen,show_source,posix_getpwuid,getpwuid,posix_geteuid,posix_getegid,posix_getgrgid,open_basedir,safe_mode_include_dir,pcntl_exec,pcntl_fork,putenv,proc_get_status,proc_nice,proc_terminate,pclose,virtual,openlog,popen,pclose,virtual,openlog,escapeshellcmd,escapeshellarg,dl,show_source,symlink,eval,mail