PHP验证码函数代码(简单实用)_PHP教程

php  
 /**
 * vCode(m,n,x,y) m个数字  显示大小为n   边宽x   边高y
 * micxp
 *jb51.net
 */ 
session_start();   
vCode(4, 15); //4个数字，显示大小为15 

function vCode($num = 4, $size = 20, $width = 0, $height = 0) {  
    !$width && $width = $num * $size * 4 / 5 + 5;  
    !$height && $height = $size + 10;   
    // 去掉了 0 1 O l 等 
    $str = "23456789abcdefghijkmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVW";  
    $code = '';  
    for ($i = 0; $i         $code .= $str[mt_rand(0, strlen($str)-1)];  
    }   
    // 画图像 
    $im = imagecreatetruecolor($width, $height);   
    // 定义要用到的颜色 
    $back_color = imagecolorallocate($im, 235, 236, 237);  
    $boer_color = imagecolorallocate($im, 118, 151, 199);  
    $text_color = imagecolorallocate($im, mt_rand(0, 200), mt_rand(0, 120), mt_rand(0, 120));   
    // 画背景 
    imagefilledrectangle($im, 0, 0, $width, $height, $back_color);   
    // 画边框 
    imagerectangle($im, 0, 0, $width-1, $height-1, $boer_color);   
    // 画干扰线 
    for($i = 0;$i         $font_color = imagecolorallocate($im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));  
        imagearc($im, mt_rand(- $width, $width), mt_rand(- $height, $height), mt_rand(30, $width * 2), mt_rand(20, $height * 2), mt_rand(0, 360), mt_rand(0, 360), $font_color);  
    }   
    // 画干扰点 
    for($i = 0;$i         $font_color = imagecolorallocate($im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));  
        imagesetpixel($im, mt_rand(0, $width), mt_rand(0, $height), $font_color);  
    }   
    // 画验证码 
    @imagefttext($im, $size , 0, 5, $size + 3, $text_color, 'c:\WINDOWS\Fonts\simsun.ttc', $code);  
    $_SESSION["VerifyCode"]=$code;   
    header("Cache-Control: max-age=1, s-maxage=1, no-cache, must-revalidate");  
    header("Content-type: image/png;charset=gb2312");  
    imagepng($im);  
    imagedestroy($im);  
} 
?>