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I have a number of scripts that echo progress as they execute because they are long running. Each basically does the following at the end of each looped row of data processed:
echo '.';
@ob_flush();
flush();
This was working just fine for years and then I upgraded to PHP 5.3.x and Apache 2.2.x across several servers. Now, even if I pad the buffer with white space or set "ob_implicit_flush(1)", I can't get it to show the output on command.
One server still shows the output, but it is in chunks. It can take nearly 5 minutes and then suddenly a string of dots appears on the screen. With the other servers, I get nothing until the script finishes executing entirely.
I've tried looking through the php.ini and httpd.conf files to see if I could figure out what had changed between the different servers, but I'm obviously missing something.
I've also tried disabling mod_deflate in .htaccess for the affected scripts, but that doesn't help either (disabling mod_gzip used to fix the problem right away).
Can someone point me in the right direction with this please? Not being able to monitor script execution in real time is causing all sorts of problems but we can't stay on these older PHP versions any longer.
On an even more peculiar side note, I did try downgrading a server to PHP 5.2.17 but the output buffer problem remained after the downgrade. This makes me suspect it is something relating to the way Apache is handling PHP output since Apache 2 was left in place.
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If you want to flush the buffered output at another time, call fflush , which is declared in the header file stdio. h . Preliminary: | MT-Safe | AS-Unsafe corrupt | AC-Unsafe lock corrupt | See POSIX Safety Concepts. This function causes any buffered output on stream to be delivered to the file.
Output buffering is a mechanism for controlling how much output data (excluding headers and cookies) PHP should keep internally before pushing that data to the client. If your application's output exceeds this setting, PHP will send that data in chunks of roughly the size you specify.
The flush() function requests the server to send its currently buffered output to the browser. The server configuration may not always allow this to happen.
The ob_start() function creates an output buffer. A callback function can be passed in to do processing on the contents of the buffer before it gets flushed from the buffer. Flags can be used to permit or restrict what the buffer is able to do.
ob_flush() (an flush()) only flush the PHP buffer - the webserver maintains a buffer itself. And weird as it may sound, flushing the buffer early actually decreases throughput on the server, hence recent versions of apache buffer more agressively. There's also horrendous problems relating to compression and partial rendering when working with HTTP chunked encoding.
If you want to incrementally add content to a page then use ajax or websockets to add it a bit at a time.
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