PHP: destructor vs register_shutdown_function

Question

I have a PHP class that creates a PNG image on the fly and sends it to browser. PHP manual says that I need to make sure that imagedestroy function is called at end

Answer 1

I recently had trouble with this as I was trying to handle destruction specifically for the case where the server experiences a timeout and I wanted to include class data in the error log. I would receive an error when referencing &$this (although I've seen it done in a few examples, possibly a version issue or a symfony side-effect), and the solution I came up with was fairly clean:

class MyClass
{
    protected $myVar;

    /**
     * constructor, registers shutdown handling
     */
    public function __construct()
    {
        $this->myVar = array();

        // workaround: set $self because $this fails
        $self = $this;
        // register for error logging in case of timeout
        $shutdown = function () use (&$self) {
            $self->shutdown();
        };
        register_shutdown_function($shutdown);
    }

    /**
     * handle shutdown events
     */
    public function shutdown()
    {
        $error = error_get_last();
        // if shutdown in error
        if ($error['type'] === E_ERROR) {
            // write contents to error log
            error_log('MyClass->myVar on shutdown' . json_encode($this->myVar), 0);
        }
    }

    ...

Hope this helps someone!