                        课程
                    
                        /后端开发
                        
                            /PHP
                        
                        /PHP实现验证码制作

一直都是提示输入错误

输入验证码一直都是显示输入错误，两个页面都有 session_start(); 大神救命~~

#form.php

<?php
error_reporting(E_ALL & ~E_NOTICE);
header("Content-type:text/html;charset=utf-8");
if(isset($_REQUEST['authcode'])){
  session_start();

if(strtolower($_REQUEST['authcode'])==$_SESSION['authcode']){
  echo'<font color="#0000CC">输入正确</font>';
}else{
  echo'<font color="#CC0000"><b>输入错误</b></font>';
}
exit();
}
?>

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8"/>
  <title>确认验证码</title>
</head>
<body>
  <form method="post" action="./form.php">
   <p>验证证图片:<img border="1" src="./captcha.php?r=<?php echo rand();?>"border="1" width="100px" height="30px"/></p>

   <p>请输入图片中的内容:<input type="text" name="authcode" value=""/></p>
<p><input type="submit" value="提交" style="padding:6px 20px;"></p>
</form>
</body>

</html>

#captcha.php

<?php

    session_start();

$image = imagecreatetruecolor(100,30);
$bgcolor=imagecolorallocate($image,255,255,255);//ffffff
imagefill($image,0,0,$bgcolor);

/*for($i=0;$i<4;$i++){
  $fontsize=6;
  $fontcolor=imagecolorallocate($image,rand(0,120),rand(0,120),rand(0,120));
  $fontcontent=rand(0,9);

  $x=($i*100/4)+rand(5,10);
  $y=rand(5,10);

  imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor);
}*/
$captch_code='';

for($i=0;$i<4;$i++){
  $fontsize=6;
  $fontcolor=imagecolorallocate($image,rand(0,120),rand(0,120),rand(0,120));

  $data='abcdefgfijklmnopqrstuvwxyz0123456789';
  $fontcontent=substr($data,rand(0,strlen($data)),1);
  $captch_code.=$fontcontent;

  $x=($i*100/4)+rand(5,10);
  $y=rand(5,10);

  imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor);
}
$SESSION['authcode']=$captch_code;

for($i=0;$i<200;$i++){
  $pointcolor=imagecolorallocate($image,rand(50,200),rand(50,200),rand(5,200));
  imagesetpixel($image,rand(1,99),rand(1,29),$pointcolor);
}
for($i=0;$i<3;$i++){
  $linecolor=imagecolorallocate($image,rand(80,220),rand(80,220),rand(80,220));
  imageline($image,rand(1,99),rand(1,29),rand(1,99),rand(1,29),$linecolor);
}

header('content-type:image/png');
imagepng( $image );