PHP OOP, how to properly use function arguments

Question

I have a little problem, I will explain everything under the code:

<?php
class Fighter {
    public $name;
    public $health = 100;
    public $power;
    public $mainhand;

    public function Punch($enemy) {
        $arm = rand(0, 1);
        if($this->mainhand == "R") {
            if($arm == 1) {
                $this->power = $this->power * 2;
            }
        }
        else if($this->mainhand == "L") {
            if($arm == 0) {
                $this->power = $this->power * 2;
            }
        }

        switch($arm) {
            case 0:
                $arm = "left";
                $this->power = rand($this->power - 2, $this->power + 2);
                echo $this->name . " hits " . $enemy . " with " . $arm . " arm and deals " . $this->power . " damage";
                break;
            case 1:
                $arm = "right";
                $this->power = rand($this->power - 2, $this->power + 2);
                echo $this->name . " hits " . $enemy . " with " . $arm . " arm and deals " . $this->power . " damage";
                break;
        }

    }
}

$fighter = new Fighter();
$fighter->name = "John";
$fighter->power = 7;
$fighter->mainhand = "R";

$enemy = new Fighter();
$enemy->name = "Matt";
$enemy->power = 6;
$enemy->mainhand = "L";

$fighter->Punch($enemy->name);
echo "<br>";
$enemy->Punch($fighter->name);
echo "<br><br>";

echo $fighter->name . " - " . $fighter->health . "HP";
echo "<br>";
echo $enemy->name . " - " . $enemy->health . "HP";

?>

Let me explain this code, here I have 2 "fighters" (objects), everything works fine, except I want to make that when for example John hits Matt, Matt will lose health, I tried doing like this:

$enemy->health = $enemy->health - $this->power;

But it doesn't work, I get errors:

Notice: Trying to get property of non-object

Warning: Attempt to assign property of non-object

Do you have any ideas how to make the code work the way I want?

In the future you should point out the lines that are causing the errors. The line numbers are in the error message. — AbraCadaver
– AbraCadaver, Commented Feb 20, 2018 at 21:22

Don't Panic · Accepted Answer · 2018-02-20 21:22:32Z

2

If you're trying to do that calculation in the Punch method, the problem is that you're not passing the Fighter object when you call Punch. You're passing the string $name property. So use

$fighter->Punch($enemy);

Instead of

$fighter->Punch($enemy->name);

If you pass the Fighter object instead, the calculation you're trying to use should work, but you'll need to make some adjustments to the output in the Punch method, e.g. using $enemy->name instead of $enemy.

echo $this->name . " hits " . $enemy->name . " with " . $arm . " arm and deals " . $this->power . " damage";
//     access the name property here ^^  since $enemy is no longer a string

If you did this by accident, you can catch the mistake earlier in the future by type hinting Fighter in the method signature.

public function Punch(Fighter $enemy) {...

edited Feb 20, 2018 at 21:22

answered Feb 20, 2018 at 21:15

Don't Panic

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2 Comments

AdrenalinMaster Over a year ago

When I do this, I get error: Catchable fatal error: Object of class Fighter could not be converted to string

AbraCadaver Over a year ago

Replace $enemy in the echo with $enemy->name

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