간단한 PHP 인증코드 생성

$image=imagecreatetruecolor(100, 30);
$white=imagecolorallocate($image, 255, 255, 2);
$red=imagecolorallocate($image, 255, 0, 0);
imagefill($image, 0, 0, $white);
//munber create
$num="";
for($i=0;$i<5;$i  ){

     $num.=rand(1,9);
}
imagestring($image, 6, rand(10,20), rand(00,10), $num,imagecolorallocate($image, rand(0,100),  rand(100,125),  rand(0,255)) );
for($j=0;$j<200;$j  ){

     imagesetpixel($image,rand(1,199), rand(1,29), imagecolorallocate($image, 255, 0, 0));
}
for($k=0;$k<5;$k  ){
imageline($image, rand(1,99), rand(1,29), rand(1,99), rand(1,29), imagecolorallocate($image,0,255, 0));
}
header("Content-type:image/png");
imagepng($image);
imagedestroy($image);
?>

인증코드, php