"ob_gzhandler" on the same server not always supported

Question

On the same hosting server, some accounts support ob_gzhandler and send the compression page to the browser:

/* Sending gz-encoded data to web browsers
 * that support compressed web pages
 */
ob_start("ob_gzhandler");

But other accounts with the code above fail and trigger the following error:

Content Encoding error

The page you are trying to open cannot be displayed because it uses an unsupported or invalid form of compression.
Contact those responsible for the site to inform them about this problem.

Question

How to discern the cause of invalid encoding error?

^{Note: The PHP configuration for both domains is rigorously the same, just like the Apache directives.}

Answer 1

For my particular case, the problem was in the definition of page headers, where we scripts with the problem of triggering the "Content Encoding" error, the headers were being set after the opening of the buffer outgoing:

ob_start("ob_gzhandler");

$expires = 2678400;
header("Pragma: public");
header("Cache-Control: maxage=".$expires);
header('Expires: ' . gmdate('D, d M Y H:i:s', time()+$expires) . ' GMT');
header('Content-Type: text/html; charset=ISO-8859-1');

To resolve, the headers were set first, and the buffer outgoing second:

$expires = 2678400;
header("Pragma: public");
header("Cache-Control: maxage=".$expires);
header('Expires: ' . gmdate('D, d M Y H:i:s', time()+$expires) . ' GMT');
header('Content-Type: text/html; charset=ISO-8859-1');

ob_start("ob_gzhandler");

Since they are old projects (+4 years), it seems that something has changed in the latest versions of PHP and the opening statement of buffer output can no longer come before the page headers.