php flush function causing weired characters on screen

Question

After so much of trouble i find out that when i use flush function in my php mail script then i get the garbage or dump characters on browser like below

The code is below

if($mail->Send()){
    echo "<br><font color=darkgreen>[$num successful send to $to]</font> ";
    // flush();
    return true;
}

If i comment that flush line then out is simple english but i uncomment that the whole pahge text looks garbage

Now is that the php problem , browser problem or server problem.

If i use the same script from shell , i mean execute inside the shell terminal then i can see the html output . but it does not work in browsers

Answer 1

I find the ANSWER to my own question ihad to turn

zlib_compression off

in my php.ini setting.

Can anyone explain what does that mean and why it worked. I had been trying this for 1 year but could not resolve the problem but now it worked