<?php  
    getValidate(100,30);  
      
    function getValidate($w,$h){  
        $img = imagecreate($w,$h);  
      
        $gray = imagecolorallocate($img,255,255,255);  
        $black = imagecolorallocate($img,rand(0,200),rand(0,200),rand(0,200));  
        $red = imagecolorallocate($img, 255, 0, 0);  
        $white = imagecolorallocate($img, 255, 255, 255);  
        $green = imagecolorallocate($img, 0, 255, 0);  
        $blue = imagecolorallocate($img, 0, 0, 255);  
        imagefilledrectangle($img, 0, 0, 100, 30, $black);  
      
      
        for($i = 0;$i < 80;$i++){  
            imagesetpixel($img, rand(0,$w), rand(0,$h), $gray);  
        }  
      
      
        $num1 = rand(1,99);  
        $num2 = rand(1,99);  
      
        imagestring($img, 5, 5, rand(1,10), $num1, $red);  
        imagestring($img,5,30,rand(1,10),getRand(), $white);  
        imagestring($img,5,45,rand(1,10),$num2, $green);  
        imagestring($img,5,65,rand(1,10),"=", $blue);  
        imagestring($img,5,80,rand(1,10),"?", $red);  
          
      
        header("content-type:image/png");  
        imagepng($img);  
        imagedestroy($img);  
    }  
    function getRand(){  
        $code = rand(0,1);  
        switch ($code) {  
            case 0:  
                return "+";  
                break;  
            case 1:  
                return "-";  
                break;  
            default:  
                # code...  
                break;  
        }  
    }  
      
    ?>