一段实用的php验证码函数

本文实例为大家分享了几段php验证码函数，都很实用，具体内容如下

代码段一：**简单php验证码函数**

    <?php

     function code(){

     $im = imagecreatetruecolor(100, 40);

     $black = imagecolorallocate($im, 0, 0, 0);

     $white = imagecolorallocate($im, 255, 255, 255);



     imagefill($im,0,0,$white);

     $strarr=array_merge(range(0,9),range(a,z),range(A,Z));

     shuffle($strarr);

     $str=join(array_slice($strarr,0,4));

     $mm=rand(0,40);

     $aaa=rand(0,0);

     $bbb=rand(0,255);

     $ccc=rand(0,255);

     $color1=imagecolorallocate($im,$aaa,$bbb,$ccc);

     imagestring($im,5,$mm,10,$str,$color1);

     for($i=0;$i<700;$i++){

       $aa=rand(0,255);

       $bb=rand(0,255);

       $cc=rand(0,255);

     $color=imagecolorallocate($im,$aa,$bb,$cc);

       $a=rand(0,100);

       $b=rand(0,40);

       imagesetpixel($im,$a,$b,$color);

     }

     for($t=0;$t<3;$t++){

       $a1=rand(0,255);

       $b1=rand(0,255);

       $c1=rand(0,255);

     $color2=imagecolorallocate($im,$a1,$b1,$c1);

       $a2=rand(0,100);

       $b2=rand(0,40);

       $a3=rand(0,100);

       $b3=rand(0,40);

       imageline($im,$a2,$b2,$b3,$b3,$color2);

     }



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

     imagepng($im);

     }

     code() ;

    ?>

代码段二：**php验证码函数**

    function _code($_code_length = 4, $_width = 75, $_height = 25){
     for($i=0;$i<$_code_length;$i++){
      $_nmsg .= dechex(mt_rand(0,15));
     }
     $_SESSION["code"] = $_nmsg;

     $_img = imagecreatetruecolor($_width, $_height);

     $_white = imagecolorallocate($_img, 250, 250, 250);

     imagefill($_img, 0, 0, $_white);

     $_gray = imagecolorallocate($_img, 196, 196, 196);

     imagerectangle($_img, 0, 0, $_width-1, $_height-1, $_gray);

     for ($i=0; $i < 6; $i++) { 
      $_md_color = imagecolorallocate($_img, mt_rand(200,255), mt_rand(200,255), mt_rand(200,255));
      imageline($_img, mt_rand(0,$_width), mt_rand(0, $_height),mt_rand(0,$_width), mt_rand(0, $_height), $_md_color);
     }

     for ($i=0; $i < 50; $i++) { 
      $_md_color = imagecolorallocate($_img, mt_rand(200,255), mt_rand(200,255), mt_rand(200,255));
      imagestring($_img, 1, mt_rand(1,$_width-5), mt_rand(1, $_height-5), "*", $_md_color);
     }

     for ($i=0; $i < $_code_length ; $i++) { 
      $_md_color = imagecolorallocate($_img, mt_rand(0,102), mt_rand(0,102), mt_rand(0,102));
      imagestring($_img, 5, $i * $_width/$_code_length+ mt_rand(1, 10), mt_rand(1, $_height/2), $_SESSION["code"][$i], $_md_color);
     }

     header("Content-Type:image/png");

     imagepng($_img);

     imagedestroy($_img);
    }

代码段三：**php图片验证码函数**

    /*@ captcha()函数的功能：生成验证码
     * @ 可自定义参数：
     * @ $width 图片宽度，默认80
     * @ $high 高度，默认25
     * @ $num 验证码个数，默认4个
     * @ $line_num 随机画线条的个数，默认10
     * @ $snow_num 随机雪花的数量，默认50
     */
    function captcha($width=80,$high=25,$num=4,$line_num=10,$snow_num=50){
     header('Content-Type:image/png');
     session_start();
     //生成随机数字＋字母
     for($a = 0;$a < $num;$a++){
      $code .= dechex(mt_rand(0, 15));//dechex ― 十进制转换为十六进制
     }
     //把生成的验证码保存在SESSION超级全局数组中
     $_SESSION['captcha'] = $code;
     //创建画布
     $img = imagecreatetruecolor($width,$high);
     //填充背景色为白色
     $backcolor = imagecolorallocate($img, '255', '255', '255');
     imagefill($img, '0', '0', $backcolor);
     //添加黑色边框
     $bordercolor = imagecolorallocate($img, 0, 0, 0);
     imagerectangle($img, 0, 0, $width-1, $high-1, $bordercolor);
     //随机画线条
     for($i=0;$i<$line_num;$i++){
      imageline($img, mt_rand(0, $width*0.1), mt_rand(0, $high), mt_rand($width*0.9, $width), mt_rand(0, $high),
      imagecolorallocate($img, mt_rand(150, 255), mt_rand(150, 255), mt_rand(150, 255)));
     }
     //随机打雪花
     for ($i=0;$i<$snow_num;$i++){
      imagechar($img,1, mt_rand(0, $width), mt_rand(0, $high),'*',
      imagecolorallocate($img, mt_rand(200, 255), mt_rand(200, 255), mt_rand(200, 255)));
     }
     //画验证码
     for ($b = 0;$b < strlen($_SESSION['captcha']);$b++){
      imagechar($img,5, $b*$width/$num+mt_rand(5,10), mt_rand(2, $high/2),$_SESSION['captcha'][$b],
      imagecolorallocate($img, mt_rand(10, 150), mt_rand(10, 150), mt_rand(0, 100)));
     }
     ob_clean();//清空输出缓冲区
     imagepng($img);
     imagedestroy($img);
    }

以上就是三段参考性较高的php验证码函数，希望对大家学习php程序设计有所帮助。