PHP User Login and logout (cookie)

Log in interface

<?PHPHeader(' Content-type:text/html;charset=utf-8 '); if(isset($_cookie[' username ']) &&$_cookie[' username ']=== ' Zeng '){        Exit(' You are already logged in, please do not log in again '); }    if(isset($_post[' Submit '])){        if(isset($_post[' username ']) &&isset($_post[' Password ']) &&$_post[' username ']== ' zengguanling ' &&$_post[' Password ']== ' 123456 ' ){            if(Setcookie(' username ',$_post[' username '], Time() +3600)){                Header(' location:skip.php?url=index.php&info= Login success! Jump to the first face after 3 seconds '); }  Else {                Echo' Cookie settings failed '; }        }  Else {            Header(' location:skip.php?url=login.php&info= Sorry, user name Live password fill error! Jump to login page in 3 seconds); }    }? ><! DOCTYPE html>Name:<input type= "text" name= "username"/>Password:<input type= "password" name= "password"/> <input type= "Submit" name= "submit" value= "Log In"/> &lt ;/form> </body>
Jump Processing Page skip.php
<? PHP     if (! isset ($_get[' url ']) | | ! isset ($_get[' Info '])) {        exit();    }? ><! DOCTYPE html>$_get[' url ']? > "/>        <title> in jump ...</title>    Echo $_get [' Info ']?></div>    </body>
Log In Home index.php
<? PHP     Header (' Content-type:text/html;charset=utf-8 ');         if (isset($_cookie$_cookie[' username ']=== ' zeng ') {        echo "Hello! {$_cookie[' username ']}, welcome back! ";         Echo "<a href= ' logout.php ' > Logout </a>";    }   Else {        echo "<a href= ' login.php ' > Please log in </a>";    }? >
Logoff Processing Interface logout.php
<?PHPHeader(' Content-type:text/html;charset=utf-8 '); if(isset($_cookie[' username ']) &&$_cookie[' username ']=== ' Zeng '){        if(Setcookie(' username ',$_post[' username '], Time()-3600)){            Header(' location:skip.php?url=index.php&info= logout success, is jumping! ‘); }Else{            Header(' location:skip.php?url=index.php&info= logoff failed, please try again later! ‘); }    }?>
PHP User Login and logout (cookie)