代码示例 $str="QWERTYUIOPASDFGHJKLZXCVBNM1234567890";

$image=imagecreate(50,25);

imagecolorallocate($image,mt_rand(0,125),mt_rand(0,125),mt_rand(0,125));

$color = imagecolorallocate($image,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

for($i=1;$i<=4;$i++) {

$date=$str[mt_rand(0,strlen($str)-1)];

$code.=$date;

}

session_start();

$_SESSION['code'] = $code;

imagestring($image,4,8,4,$code,$color);

for($i=1;$i<=30;$i++) {

imagesetpixel($image,mt_rand(0,50),mt_rand(0,25),mt_rand(125,200));

}

for($i=1;$i<=mt_rand(1,5);$i++) { imageline($image,mt_rand(0,50),mt_rand(0,25),mt_rand(0,50),mt_rand(0,25),mt_rand(100,150)); } header("content-type:image/png"); imagepng($image); ?>

数字+字母验证码(各字母颜色不同)：

$str="QWERTYUIOPASDFGHJKLZXCVBNM1234567890";

$image=imagecreate(50,25);

imagecolorallocate($image,mt_rand(0,125),mt_rand(0,125),mt_rand(0,125));

$color[0] = imagecolorallocate($image,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

$color[1] = imagecolorallocate($image,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

$color[2] = imagecolorallocate($image,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

$color[3] = imagecolorallocate($image,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

for($i=0;$i<4;$i++) {

$date=$str[mt_rand(0,strlen($str)-1)];

$code.=$date;

imagestring($image,5,6+$i*10,4,$code[$i],$color[$i]);

}

session_start();

$_SESSION['code'] = $code;

for($i=1;$i<=30;$i++) {

imagesetpixel($image,mt_rand(0,50),mt_rand(0,25),mt_rand(125,200));

}

for($i=1;$i<=mt_rand(1,5);$i++) {

imageline($image,mt_rand(0,50),mt_rand(0,25),mt_rand(0,50),mt_rand(0,25),mt_rand(100,150));

}

header("content-type:image/png");

imagepng($image);