Gzip output handler - `ob_end_flush()` must not call `flush()`

Description

This issue is problematic only when zlib.output_compression is enabled.

Currently, when zlib.output_compression is enabled like:

php -S 127.0.0.1:81 -d zlib.output_compression=1 -t .

(but also tested if enabled when used /w Apache /wo mod_deflate)

and ob_end_flush() is called, no headers cannot be send anymore even if the nothing was output.

Currently, we had to use the following code

while (ob_get_level() > 0) {
    if (ob_get_length() === 0) {
        ob_end_clean();
    } else {
        ob_end_flush();
    }
}

to workaround.

When zlib.output_compression is NOT enabled, the following code:

while (ob_get_level() > 0) {
    ob_end_flush();
}

is working (allows to send additional headers).

Because of this inconsistency, I belive php gzip output handler behaviour should be fixed, when output buffer is empty, to not flush implicitly.

PHP Version

any

Operating System

any

Reproduisez le comportement avec la commande PHP CLI fournie, en comparant un tampon de sortie vide avec un tampon contenant une sortie et en vérifiant si les headers peuvent encore être envoyés. Examinez ensuite le chemin ob_end_flush() et le gestionnaire de sortie zlib ; c’est terminé lorsqu’un tampon vide ne déclenche pas implicitement de flush, tandis qu’une sortie non vide conserve son comportement attendu.