一段实用的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() ; ?>

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);}

/*@ 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);}