php验证码之数字运算验证码

 
<?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;
    }
}
  
?>