How to bring in the proper form? php basic oop

Question

the problem is this, I'm doing a task to understand the syntax of php + basic oop syntax. The meaning of the task is to create a developer class that implements the primate interface and inherits the abstract developer class, it also inherits the plankton trait that can drink coffee. Here is my code

declare(strict_types=1);

interface Primat {
    public function eat(bool $e);
    public function drink(bool $d);
}
trait ofPlank{
    function cofeeTime($cof){ echo 'drink cofee ';}
}

abstract class Human{
    public string $name;
    abstract public function work(string $work);
}


class Dev extends Human implements primat{
    use ofPlank;
    public  $rank = array(
        1=>'junior',
        2=>'middle',
        3=>'senior',
        4=>'lead'
    );
        public int $rankState = 0;

        public function __construct(int $currentRank)
        {
      $this->rankState = $currentRank;
            }
    public function show()
    {
        echo $this->rank[$this->rankState];
    }

    public function Up()
    {
        $this->rankState++;
    }

    public function Down()
    {
        $this->rankState--;
    }



public function eat( $e)
{
    if ($e ==1){
   echo 'eat';}
    else {
        echo 'hungry';
    }


    // TODO: Implement eat() method.
}
public function drink($d)
{
    if ($d ==1){
        echo 'drink';}
    else {
        echo 'need water';
    } ; // TODO: Implement drink() method.
}
  use ofPlank;
    public function work($work)
    {
        $work = 'go to work';
        // TODO: Implement work() method.
    }


} echo 'backend promotion from';
$backend = new Dev(1,);
echo $backend->show()."\n";
$backend->Up();
echo 'to ';
echo $backend->show()."\n";
echo '|backend need eat->';
$backend->eat($e=1);
//var_dump($backend);
echo '|ofplank    ';
$backend->cofeeTime(cof );
?>
<br><?php
echo 'frontend lvl  ';
$frontend = new dev(1,);
echo $frontend->show()."\n";
echo '|frontend need water->';
$backend->drink($d=2);
?>
<br>
<br>
<br>
<br>
<br>

I would like to know how this code can be improved? Does this code fit the definition of the simplest OOP? what did done wrong on psr 1-2? And finally, how can the work method accept a work instance parameter? Thanks in advance to everyone who gives me their time!