Can I use a function to return a default param in php?

I would like to do something like this:

function readUser($aUser = loadDefaultUser()){

 //doing read User
}

I find that it will display a error to me, how can I pass a function return as a default value? Thank you.

Answer

Yes, you can provide a default argument. However, the default argument "must be a constant expression, not (for example) a variable, a class member or a function call."

You can fake this behaviour by using some constant value for the default, then replacing it with the results of a function call when the function is invoked.

We'll use NULL, since that's a pretty typical "no value" value:

function readUser($aUser = NULL) {
    if (is_null($aUser))
        $aUser = loadDefaultUser();

    // ... your code here
}