output_buffer – PHP Stream Filter Extension

Buffers write operations on any PHP stream, reducing syscall overhead exactly as ob_start() does for output – but for arbitrary streams.

• PHP 8.0 or higher
• php-dev / php-devel package
• Standard C build tools (gcc / clang, make, autoconf)

cd output_buffer_ext/
phpize
./configure --enable-output_buffer
make
sudo make install          # installs output_buffer.so into the PHP ext dir

Add to php.ini:

extension=output_buffer

Use the PHP SDK and run:

buildconf
configure --enable-output_buffer=shared
nmake

No stream_filter_register() call needed – the filter is registered automatically when the extension loads.

$fp = fopen('output.txt', 'w');

// default 4 KB buffer
stream_filter_append($fp, 'output.buffer');

// custom 8 KB buffer
stream_filter_append($fp, 'output.buffer', STREAM_FILTER_WRITE, 8192);

for ($i = 0; $i < 10000; $i++) {
    fwrite($fp, 'x');     // ~3 real writes instead of 10 000
}

fclose($fp);              // remaining bytes flushed automatically

fflush($fp) is also supported – the buffer is flushed immediately.

output.buffer