test.php

<?php

interface fooplan
{
  function getReverseName();
}

class foo implements fooplan
{
	  private $name;
 
    public function __construct($name = 'Frank')
    {
    	$this->name = (string)$name;
    }
 
    public function getReverseName()
    {
    	return $this->strrev($this->name);
    }
}
 
$bar = new foo('Jim');
print $bar->getReverseName();

test2.php

<?php

namespace My\Fancy\ClassName\Prefix;

class WontWork {

}

class OnlyFqcnWillWork {

}

// false
class_exists('WontWork');

// true
class_exists('My\Fancy\ClassName\Prefix\OnlyFqcnWillWork');

test4.php

<?php

trait foo
{
  public function doSomething()
  {
    echo 'Done';
  }
}

class bar {
  use foo;
  
  public function doSomethingElse()
  {
    echo 'Done';
  }
}

$bar = new bar;
$bar->doSomething();