?

如果有什么好的提议，可以留言，一起改善代码：

<?php  
//$i为要写在画板的位置，$num为要写的文字  
function rand4string($i,$num){  
    global $image_width,$image_height,$img;  
    $font=mt_rand(3,5);  
    $x=mt_rand(1,8)+$image_width*$i/6;  
    $y=mt_rand(1,$image_height/4);   
    $color=imagecolorallocate($img,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200));  
    imagestring($img,$font,$x,$y,$num,$color);  
}  
session_start();  
header("content-type:image/png");  
$image_width=80;  
$image_height=18;  
$img = imagecreate($image_width,$image_height);  
imagecolorallocate($img,255,255,255);  
$random4symbol = array("+","-","x");    //三个符号进行循环  
$result = 0;  
$symbol = $random4symbol[mt_rand(0,count($random4symbol)-1)];  
$num1 = mt_rand(1,9);  
rand4string(0,$num1);  
$num2 = mt_rand(1,9);  
switch ($symbol){  
    case "+":  
        $result = $num1 + $num2;  
        rand4string(1,"+");  
        break;  
    case "-":  
        $result = $num1 - $num2;  
        rand4string(1,"-");  
        break;  
    case "x":  
        $result = $num1 * $num2;  
        rand4string(1,"x");  
        break;  
}  
rand4string(2,$num2);  
rand4string(3,"=");  
rand4string(4,"?");  
$_SESSION['code'] = $result;  
imagepng($img);  
imagedestroy($img);  
?>  

?

打完收工。。呵呵。