<?php  
 /**
 * vCode(m,n,x,y) m個數(shù)字  顯示大小為n   邊寬x   邊高y
 * micxp
 *jb51.net
 */ 
session_start();   
vCode(4, 15); //4個數(shù)字，顯示大小為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 < $num; $i++) {  
        $code .= $str[mt_rand(0, strlen($str)-1)];  
    }   
    // 畫圖像 
    $im = imagecreatetruecolor($width, $height);   
    // 定義要用到的顏色 
    $back_color = imagecolorallocate($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));   
    // 畫背景 
    imagefilledrectangle($im, 0, 0, $width, $height, $back_color);   
    // 畫邊框 
    imagerectangle($im, 0, 0, $width-1, $height-1, $boer_color);   
    // 畫干擾線 
    for($i = 0;$i < 5;$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), $font_color);  
    }   
    // 畫干擾點 
    for($i = 0;$i < 50;$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), $font_color);  
    }   
    // 畫驗證碼 
    @imagefttext($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);  
} 
?>