Redirect Function Php

I have a function, 'redirect_to()' written on php script that is called after a successful update to a page on my custom CMS. It works fine on the localhost, but when I try it on my actual live domain I get the following error message:

Warning: Cannot modify header information - headers already sent by (ou开发者_StackOverflow中文版tput started at /hermes/bosweb/web119/b1192/ipg.typaldosnetcom/edit_listing.php:7) in /hermes/bosweb/web119/b1192/ipg.typaldosnetcom/includes/functions.php on line 20

Here is the code for the redirect_to() function:

function redirect_to ($location = NULL) {
    if ($location != NULL) {
        header("Location: {$location}");
        exit;
    }
}

I've made sure to call the function before I output any HTML, so I'm not sure what the problem really is.

My question: Why am I receiving this error?

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It's not lying. You've output something before getting to this point. Check the locations mentioned in the error messages.

Show us the first 25 lines of each of the files mentioned.

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you already sent your output to the page before you set the header. first you need to set the headers and then can the output come.

It can even be a whitespace.

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It means something was already outputted on the suggested line. Try going there and see what it does.

Try pasting the surrounding code on that position for a better clarification if you can't find the problem yourself.

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One common cause is to have a line after a php file you're including...

Simple solution: remove the closing php tag "?>" from all files as it's not needed..

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You can test if you have a character before the opening php-script tag by removing any closing php-script tag. This way you are sure there isn't any character left (it's not needed).

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Use output buffering:

<?php 
ob_start();

// Test buffered output. 
echo 'hello world'; 

function redirect_to ($location = NULL) {
    if ($location != NULL) {
        header('Location: ' . $location);
        exit;
    }
}

// rest of php file here

ob_end_flush();
?>

Docs: ob_start() and ob_end_flush()