PHP函数参数my_func（$ param =''）

Question

I saw some PHP today I don't understand, can anyone explain it to me?

function my_func($param='')
{

    if (empty($param))
    {
        return false;
    }
    else
    {
        return true;
    }
}

What I don't understand is the $param variable being assigned an empty string but somehow not being empty inside the function? Is this just a default value?

Answer 1

my_func("string") //makes $param "string"

my_func() //picks default making $param ''

You can have required and optional params like

function my_func($param1, $param2='default')

You can NOT put optional params behind required params

function my_func($param1='', $param2) //gives errors.