PHP callback in browser window

Solution:

This is likely because of output buffering.

Output buffering is a mechanism in PHP that holds the output in memory until a later call toflush the buffer (also happens automatically when the script shuts down).

Output buffering allows you to print content inside of your script, and provide changes to HTTP headers after content has been printed. Normally, once you print content and send it to apache (who, in turn, sends it back to the client), you can no longer modify the HTTP headers. With output buffering, PHP will store this output in memory and won't hand it over to apache until you tell it to.

You should be able to get this to work in one of four ways:

• ob_end_clean at the very top of your PHP script to disable output buffering
• Disableoutput_buffering in php.ini
• Enableimplicit_flush in php.ini (not recommended since it makesoutput_buffering pointless
• Callob_flush after yourprint/echo statements

Note: There are also other very legitimate uses for output buffering, such as templating - but that's not important here.

With that being said

This won't necessarily work for everyone. Some browsers by default, and others by configuration, won't start loading a page until the connection is closed and all HTML content has been received. If you want this to work across most every browser today - you might be better off making AJAX calls back to your server.

Edit: To tell ifoutput_buffering is on, a simple call toprint ob_get_level() will tell you. If that prints a number > 0,output_buffering is the culprit.

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