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() ;
  
?>