dsyak22488 2017-04-12 02:19
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PHP：为什么我的cookie没有正确设置？

What's wrong with my code? When I run it, it tells me: "Notice: Undefined index: visits" on the lines if($_COOKIE["visits"] == 1) and $numOfVisits = $_COOKIE["visits"]; in the body section.

<!DOCTYPE html>

<?php 
if (!isset($_COOKIE["visits"])) 
    setcookie("visits", 1, time()+3600*24*365);
else{
    $visits = $_COOKIE["visits"] + 1;
    setcookie("visits",$visits, time()+3600*24*365);
}
?>

<html lang="en">
    <head>
        <title>numOfVisits</title>
        <meta charset="utf-8"/>
    </head>
    <body>
        <?php
        if($_COOKIE["visits"] == 1)
            echo("Welcome to my webpage! It is your first time that you are here.");
        else{
            $numOfVisits = $_COOKIE["visits"];
            echo("Hello, this is the #$numOfVisits time that you are visiting my webpage.");
        }
        ?>
    </body>
</html>
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  • douzhao9608 2017-04-12 02:28
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    The problem is that you can only set cookies or start sessions before any headers are send from the server to the client. (See documentation on setcookie)

    setcookie() defines a cookie to be sent along with the rest of the HTTP headers. Like other headers, cookies must be sent before any output from your script (this is a protocol restriction). This requires that you place calls to this function prior to any output, including and tags as well as any whitespace.

    What this means in practise is that you can't set a cookie after you already output something. In this case you're outputting <!doctype html> before you are setting the cookie.

    The solution is to set the cookie before you output any HTML.

    So solution:

    <?php 
if (!isset($_COOKIE["visits"])) 
    setcookie("visits", 1, time()+3600*24*365);
else{
    $visits = $_COOKIE["visits"] + 1;
    setcookie("visits",$visits, time()+3600*24*365);
}
?>
<!doctype html>
...
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