How can the location of the first output causing the header error be identified in a PHP script?

To identify the location of the first output causing the header error in a PHP script, you can use the headers_list() function to check for any headers that have already been sent before calling the header() function. This will help you pinpoint the exact location in your script where the output is being sent to the browser before setting headers. 

if (headers_sent()) {
    $headers = headers_list();
    foreach ($headers as $header) {
        echo $header . "<br>";
    }
    die("Headers already sent, cannot send new headers");
}

// Your PHP code here
// Make sure no output is sent before setting headers

header("Location: https://www.example.com");
exit;

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