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