php 验证码 ucode

<?php
//验证码
function ucode($length=4,$mode=1,$type='png',$width=48,$height=22) 
{
    $randval = rand(1000,9999);
    $_SESSION['IMGCODE']= $randval;

    $width = ($length*9+10)>$width?$length*9+10:$width;
    if ( $type!='gif' && function_exists('imagecreatetruecolor')) {
        $im = @imagecreatetruecolor($width,$height);
    }else {
        $im = @imagecreate($width,$height);
    }
    $r = Array(225,255,255,223);
    $g = Array(225,236,237,255);
    $b = Array(225,236,166,125);
    $key = mt_rand(0,3);

    $backColor = imagecolorallocate($im, $r[$key],$g[$key],$b[$key]);    //背景色（随机）
    $borderColor = imagecolorallocate($im, 100, 100, 100);                    //边框色
    $pointColor = imagecolorallocate($im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));                 //点颜色

    @imagefilledrectangle($im, 0, 0, $width - 1, $height - 1, $backColor);
    @imagerectangle($im, 0, 0, $width-1, $height-1, $borderColor);
    $stringColor = imagecolorallocate($im,mt_rand(0,200),mt_rand(0,120),mt_rand(0,120));
    // 干扰
    for($i=0;$i<10;$i++){
        $fontcolor=imagecolorallocate($im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
        imagearc($im,mt_rand(-10,$width),mt_rand(-10,$height),mt_rand(30,300),mt_rand(20,200),55,44,$fontcolor);
    }
    for($i=0;$i<25;$i++){
        $fontcolor=imagecolorallocate($im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
        imagesetpixel($im,mt_rand(0,$width),mt_rand(0,$height),$pointColor);
    }

    @imagestring($im, 5, 5, 3, $randval, $stringColor);
    output($im,$type);
}
/**
 * 打印验证码
 *
 * @param unknown_type $im
 * @param unknown_type $type
 */
function output($im,$type='png') 
{
    header("Content-type: image/".$type);
    $ImageFun='Image'.$type;
    $ImageFun($im);
    imagedestroy($im);  
}

直接执行ucode()会产生一个img标签显示在页面上

结果：