如何使用覆盖方法在PHP中显示setter内容？

this is my code:

<?php
    class person {
                var $name;      
                function __construct($persons_name) {
                        $this->name = $persons_name;
                }

                public function get_name() {
                        return $this->name;
                }
                protected function set_name($new_name) {
                    if ($this->name !=  "Jimmy Two Guns") {
                        $this->name = strtoupper($new_name);
                    }
                }
    }
    class employee extends person {
        protected function set_name($new_name) {
                if ($new_name ==  "Stefan TRALA") {
                    $this->name = $new_name;
                }

                else if ($new_name ==  "Johnny Fingers") {
                    person::set_name($new_name);
                }        
        }

        function __construct($employee_name) {
                $this->set_name($employee_name);
        }
    }

    $empl = new employee;
    echo $empl->set_name("Stefan TRALA");
?>

Im getting this warning: Warning: Missing argument 1 for employee::__construct() WHY ? why my echo does not work ? What did I write wrong ? Thank you!

Your constructor takes one argument, so it should be:

$empl = new employee("Stefan TRALA");

Then you can remove echo $empl->set_name() since it is already called in the constructor.

how to get the name?

add this function:

function get_name(){
  return $this->name;
}

then use it:

echo $empl->get_name();

Your class expects the person's name as the first argument:

function __construct($persons_name) {

Yet you call it without:

$empl = new employee;

You should either make the name optional:

function __construct($persons_name = '') {

Or pass it in on creation:

$empl = new employee('Joe');

You have declared a constructor function as part of your class. Constructor functions are called immediately upon class instantiation, please observe:

$empl = new employee;

This is instantiating the class, which will immediately call the following:

function __construct($employee_name) {
    $this->set_name($employee_name);
}

Obviously, we need to pass in an argument to this function initially otherwise we will get that error.

$empl = new employee("Stefan TRALA");

If you need to change it later, you can with set_name, but it must be supplied initially.

Alternatively, you can modify the parent constructor function to expect a null but accept a proper argument:

function __construct($persons_name = null)

Your constructor takes an argument ($employee_name)

So you need to instantiate your employee using $empl = new employee("Stefan TRALA");

But also your echo statement is calling a function with no return value. You need to use the get_name function, not set_name, to return the value.

echo $empl->get_name();

The error in your code is not about setters, you are not specifying the parameter at the constructor.

Your code:

$empl = new employee;
echo $empl->set_name("Stefan TRALA");

Is the same as:

$empl = new employee();
echo $empl->set_name("Stefan TRALA");

The fix:

$empl = new employee("Stefan TRALA");
// this works, but, no longer necesarilly
//echo $empl->set_name("Stefan TRALA");

Remember, every time you use the "new" keyword, you are executing a constructor.

And, constructors are written like this:

$empl = new employee("Stefan TRALA");

But, should be read (not written) as this:

$empl = new employee; $empl->__construct("Stefan TRALA");

The error is not at the "setter".

Cheers.