Write to file with register_shutdown_function

Question

Is it possible to do the following?

register_shutdown_function('my_shutdown');
function my_shutdown ()
{
    file_put_contents('test.txt', 'hello', FILE_APPEND);
    error_log('hello', 3, 'test.txt');
}

Doesn't seem to work. BTW i'm on PHP 5.3.5.

Answer 1

It depends which SAPI you are using. The documentation page for register_shutdown_function() states that under certain servers, like Apache, the working directory of the script changes.

The file gets written, but not where your .php file is (DocumentRoot), but in the folder of the Apache server (ServerRoot).

To prevent this, you need to some sort of hotwire the working folder changes. Just when your script starts executing (in the first few lines), you need to somehow store the real working folder. Creating a constant with define() is perfect for this.

define('WORKING_DIRECTORY', getcwd());

And you need to modify the shutdown function part like this:

function my_shutdown ()
{
    chdir(WORKING_DIRECTORY);

    file_put_contents('test.txt', 'hello', FILE_APPEND);
    error_log('hello', 3, 'test.txt');
}

register_shutdown_function('my_shutdown');

This way, the working folder will instantly be changed back to the real one when the function is called, and the test.txt file will appear in the DocumentRoot folder.

Some modification: It is better to call register_shutdown_function() after the function has been declared. That's why I wrote it below the function code, not above it.