I got this error after running the following function:
function send_buffer(){
ob_end_flush();
ob_flush();
flush();
ob_start();
}
The main body of my website takes a few seconds to load, so I want to send the header first. But I got the following error: Notice: ob_flush() [ref.outcontrol]: failed to flush buffer zlib output compression
You can't use gzip/zlib compression as well as flush.
Pick one or the other. I'd recommend gzip rather than flush.