如何判断是否从输出缓冲回调中调用了该函数？

In a function, how can I find out if it's been called from an output buffering callback (not necessarily directly)?

function foo() {
    if (magic here ????)
        $log->write("foo:Callback") 
    else
        $log->write("foo:Normal")
}

function calls_foo() {
    ...stuff
    foo();
}

calls_foo() // should log foo:Normal

ob_start('calls_foo')

    ...stuff

// should log foo:Callback at the end of the script

Check $debug = debug_backtrace(). If the debug array is 1 long then you get called from main which means this is an ob callback called at the end of the request. Then you can iterate the array and look at the 'function' key of each array for an ob flushing function.

The function ob_get_status() returns an array containing information on the current status of output buffering.