PHP simple image verification code implementation

//The first code generates random pictures------code2.php

//Open session to save the generated content
session_start();
$table=array (
 "pic0"=>"dog",
 "pic1"=>"cat",
 "pic2"=>"fish",
 "pic3"=>"bird"
);
$index =rand(0,3);
$value=$table['pic'.$index];
$_SESSION['authcode']=$value;
//Get the randomly generated picture name
$filename=dirname( __FILE__).'/pic'.$index.'.jpg';
$content=file_get_contents($filename);
header('Content-type:image/jpg');
echo $content;
?>

//Verification of the second code solid line form

if(isset($_REQUEST['authcode'])){
session_start();
if($_REQUEST['authcode' ]==$_SESSION['authcode']){
echo "right";
}else{
echo "sad story";
echo $_REQUEST['authcode'];
}
}
? >







 picture:

 //Switch to another image through js
 change picture
 words:< ;input type="text" name="authcode" value="" />




?>

/*The path of the code is the path of linux*/

Verification code, PHP