求一段产生随机数字的程序(急急急急急)

Question

$char = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; //这个串可任意给出
for($i=0;$i<4;$i++) {
  srand((double)microtime()*1000000);
  $s .= $char[rand(0, strlen($char)-1)];
}
Header("Content-type: image/gif");
$im = imagecreate(40,20);
$black = ImageColorAllocate($im, 0,0,0);
$white = ImageColorAllocate($im, 255,255,255);
imagestring($im, 4, 2, 1, $s, $white);
Imagepng($im);
ImageDestroy($im);

Answer 1

<?session_start();?> 
<FORM METHOD=POST ACTION=""> 
<input type=text name=number maxlength=4><img src="YanZhengMa.php?act=init"> 
<INPUT TYPE="submit" name="sub"> 
</FORM> 
<? 
//检验校验码 
if(isset($HTTP_POST_VARS["sub"])): 
if($HTTP_POST_VARS["number"] != $HTTP_SESSION_VARS[login_check_number] || empty($HTTP_POST_VARS["number"])){ 
    echo "校验码不正确!" ; 
}else{ 
    echo"验证码通过！"; 
} 
endif; 
show_source('test.php'); 
//以上本页的源码 
//以下是生成验证码的源码 
show_source('YanZhengMa.php'); 
?> 
<?php 
session_start(); 
session_register("login_check_number"); 
//昨晚看到了chianren上的验证码效果，就考虑了一下，用PHP的GD库完成了类似功能 
//先成生背景，再把生成的验证码放上去 
$img_height=120;    //先定义图片的长、宽 
$img_width=40; 
if($HTTP_GET_VARS["act"]== "init"){ 
    //srand(microtime() * 100000);//PHP420后，srand不是必须的 
    for($Tmpa=0;$Tmpa<4;$Tmpa++){ 
        $nmsg.=dechex(rand(0,15)); 
    }//by sports98 
    $HTTP_SESSION_VARS[login_check_number] = $nmsg;     //$HTTP_SESSION_VARS[login_check_number] = strval(mt_rand("1111","9999"));    //生成4位的随机数，放入session中 
    //谁能做下补充，可以同时生成字母和数字啊？？----由sports98完成了     $aimg = imageCreate($img_height,$img_width);    //生成图片 
    ImageColorAllocate($aimg, 255,255,255);            //图片底色，ImageColorAllocate第1次定义颜色PHP就认为是底色了 
    $black = ImageColorAllocate($aimg, 0,0,0);        //定义需要的黑色 
    ImageRectangle($aimg,0,0,$img_height-1,$img_width-1,$black);//先成一黑色的矩形把图片包围     //下面该生成雪花背景了，其实就是在图片上生成一些符号 
    for ($i=1; $i<=100; $i++) {    //先用100个做测试 
        imageString($aimg,1,mt_rand(1,$img_height),mt_rand(1,$img_width),"*",imageColorAllocate($aimg,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255))); 
        //哈，看到了吧，其实也不是雪花，就是生成＊号而已。为了使它们看起来"杂乱无章、5颜6色"，就得在1个1个生成它们的时候，让它们的位置、颜色，甚至大小都用随机数，rand()或mt_rand都可以完成。 
    }     //上面生成了背景，现在就该把已经生成的随机数放上来了。道理和上面差不多，随机数1个1个地放，同时让他们的位置、大小、颜色都用成随机数~~ 
    //为了区别于背景，这里的颜色不超过200，上面的不小于200 
    for ($i=0;$i<strlen($HTTP_SESSION_VARS[login_check_number]);$i++){ 
        imageString($aimg, mt_rand(3,5),$i*$img_height/4+mt_rand(1,10),mt_rand(1,$img_width/2), $HTTP_SESSION_VARS[login_check_number][$i],imageColorAllocate($aimg,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200))); 
    } 
    Header("Content-type: image/png");    //告诉浏览器，下面的数据是图片，而不要按文字显示 
    ImagePng($aimg);                    //生成png格式嘿嘿效果蛮像回事的嘛 
    ImageDestroy($aimg); 
} ?>

Answer 2

随机串改进一下$aKey = array("a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","`","~","!","@","#","$","%","^","&","*","(",")","_","+","=","-","\\","|","]","[","{","}",":",";","'","\"","<",">",",",".","?","/");
$s = join(array_rand(array_flip($aKey),5));