PHP Should I use ob_clean after ob_start

问题

I made a simple login-system in php and mysql, but I keep getting errors saying that headers already been sent, and using ob_start fixes this problem, but im not sure if I should then use ob_clean at the footer afterward?

Also, the error comes when I have logged in to the account page, saying header already been sent in previuos page - > header("Location: account.php"); But I have to redirect the user when they login.

My login page looks like this

require_once('models/init.php');  // db connection and other functions
include('header.php');  // some html code for the header, with one line php-function to check if user is logged in, if so show "home" tab instead of "login"


{ 

  php code to check if username/pass matches etc, and if so redirect to account page

  header("Location: account.php");

}

 echo "<form>" // display the login form

include("footer"); // including footer, some html/js code.

This code above works if I use ob_start in the header.php file. But should I use ob_clean afterwards in the footer.php file?

Sorry if anything is unclear, english is not my first languish

Thanks!

回答1:

The general principle is you cannot use echo before header(). So, this will never work:

echo "this is my header";
header("Location: account.php");
echo "this is my footer";

However, if you sent the headers first, everything works fine:

header("Location: account.php");
echo "this is my header";
echo "this is my footer";

In your case, you should do the check before you include the header:

require_once('models/init.php');  // db connection and other functions

if ($user_is_logged_in) { // Do your check here
    header("Location: account.php");
}

include('header.php');  // some html code for the header, with one line php-function to check if user is logged in, if so show "home" tab instead of "login"
echo "<form>" // display the login form
include("footer"); // including footer, some html/js code.

回答2:

ob_start() captures the output (what would otherwise be printed or echoed). If you don't need to echo the output or to do anything with it then just use ob_end_flush() when you are finished.

来源：https://stackoverflow.com/questions/19139521/php-should-i-use-ob-clean-after-ob-start

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php

mysql

header

ob-start