[OOP Interfaces] Object-Oriented Programming: Understanding Interfaces

00-Cache.php

<?php

class Cache 
{
  public function set($key, $value) 
  {
    // method implementation
  }
}

01-Cache.php

<?php

class Cache 
{
  public function set($key, $value) {
    set_transient($key, $value);
  }
}

02-CacheInterface.php

<?php

interface iCache 
{
  public function set($key, $value);
  public function get($key);
  public function has($key);
}

03-SimpleCache.php

<?php

interface iCache {
  public function set($key, $value);
  public function get($key);
  public function has($key);
}

public class SimpleCache implemnents iCache
{
  public function set($key, $value)
  {
    set_transient($key, $value, DAY_IN_SECONDS);
  }
  
  public function get($key)
  {
    if (!$this->has($key))
    {
      return false;
    }
    return get_transient($key);
  }
  
  public function has($key)
  {
    return false !== get_transient($key);
  }
}