PHP定义一个变量，如果它没有传递给函数

Question

How can I set a default variable to a function in PHP? In python, it would look like this:

def fun(con = predefined):

I've tried the following to no avail:

function fun($con = $GLOBALS['con']){}

In this instance, as you can see, I would like to set the value to the definition of a global variable.

Answer 1

Looks like your problem is that you're trying to set a default from a global. PHP may not like this. You can circumvent it this way:

function fun($con = null){
    $con or $con = $GLOBALS['con'];
}

I personally think this is kind of hokey. It looks like you're wanting to get a DB connection from a global resource. I don't think that's how this should be done, but this answer would allow $con to be set from global if not passed to the function. Or allow it to be used if passed.