What is the difference b/w Countable and Non Countable Objects

问题

I am trying out to find difference b/w a countable and a non countable object

First I found out the Type of object

echo gettype($data["current_fiat_currency"]);

Which is a Object

But when i had checked that it is a countable object or not

var_dump($data["current_fiat_currency"] instanceof Countable );

then it returns

 False

Below is the object content

var_dump($data["current_fiat_currency"]);

object(stdClass)[2010]
  public 'id' => string '1399' (length=4)
  public 'currency_name' => string 'US Dollar' (length=9)
  public 'currency_slug' => string '' (length=0)
  public 'currency_code' => string 'USD' (length=3)
  public 'currency_logo' => string '0' (length=1)
  public 'currency_type' => string '3' (length=1)
  public 'logo' => string '.png' (length=4)
  public 'exe' => string '0' (length=1)
  public 'logo_exe' => string '1' (length=1)
  public 'symbol_native' => string '$' (length=1)
  public 'symbol' => string '$' (length=1)
  public 'name_plural' => string 'US dollars' (length=10)
  public 'market_cap' => string '0' (length=1)
  public 'circulating_supply' => string '0' (length=1)
  public 'max_supply' => string '0' (length=1)
  public 'total_supply' => string '0' (length=1)
  public 'cryptoid_info_exe' => string '0' (length=1)
  public 'show_on_website' => string '1' (length=1)
  public 'default_selected' => string '1' (length=1)
  public 'exchange_rate' => string '1' (length=1)
  public 'currencies_stats_exe' => string '0' (length=1)
  public 'currencies_stats_last_updated' => null
  public 'mineable_or_not' => string '0' (length=1)
  public 'show_on_top_bar' => string '0' (length=1)
  public 'added_date' => string '2018-01-11 05:21:37' (length=19)
  public 'graph_size_chart_status' => string '0' (length=1)
  public 'twitter' => null
  public 'reddit' => null
  public 'status' => string '1' (length=1)
  public 'for_pair_status' => string '0' (length=1)

So how i can convert a existing object to countable if it is not countable according to Php 7.2 because my codes working fine with Php 7.0.

回答1:

A hack may be

echo count((array) $data["current_fiat_currency"]);

It's just a patching solution and I think it'll work in just some cases and you should not rely on it.

回答2:

An object is Countable when is implementing the interface Countable.

That interface is defining a public contract for a countable objects. That means that as part of the contract, implies that your class must implement the method $object.count().

The difference is that an object that implements the Countable interface, means that you can execute count PHP native methods like count() passing as parameter your object, having as a result the value you define on the method implemented. For instance, for a non countable object you will get a warning.

回答3:

In order to make an object countable, it has to implement the interface countable and have a count method. I.e.

class YourObject implements Countable 
{

    private $whatYouWantToCount = 0;

    public function count() 
    { 
        return $this->whatYouWantToCount; 
    } 
} 

Source http://php.net/manual/en/class.countable.php

来源：https://stackoverflow.com/questions/52815632/what-is-the-difference-b-w-countable-and-non-countable-objects