rfc:instance_counter

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PHP RFC: instance counter

Introduction

Coming to Object-Orientated Programming, PHP offers a variety of possibilities to obtain information about classes and their instances (objects). In this regard, the classes/objects functions (http://www.php.net/manual/en/ref.classobj.php) as well as the reflection API (http://www.php.net/manual/en/book.reflection.php) do a great job. But still there is no function to obtain a particular information: the number of instances of a class.

One might say, simply implement a static counter in each class. But what about built-in classes like SPL? A wrapper would be required. Implementing it these ways, it does not only sound, but it actually is cumbersome. The purpose of this RFC is to address this issue.

Proposal

The proposal is to add a new function returning an array ('name of the class' ⇒ number of instances) in the current script.

The function name should fit in with the current names of class/object functions. Therefore, the name get_objects_count() seems to be reasonable, but is still up for discussion (see Function name).

Example #1:

print_r (get_objects_count());
// Array ()
 
$foo = new stdClass;
 
print_r (get_objects_count());
// Array ( [stdClass] => 1 )
 
$bar = new stdClass;
 
print_r (get_objects_count());
// Array ( [stdClass] => 2 )
 
$bar = null;
 
print_r (get_objects_count());
// Array ( [stdClass] => 1 )
 
$foo = null;
 
print_r (get_objects_count());
// Array ()

Use cases:

  • Debugging
  • Implementation of design patterns (f.ex. flyweight pattern)
  • Extended control: limit the number of objects
  • to be continued…

Function name

Further suggestions for the function name in example #1:

// Proposed
get_objects_count()

// Alternatives
get_instances_counts()
get_instances_count()
get_instance_counts()
get_object_store_count()
get_class_counts() 

Backward Incompatible Changes

No BC breaks.

Proposed PHP Version(s)

next PHP 5.4.x or PHP 5.5.x

SAPIs Impacted

None.

Impact to Existing Extensions

None.

New Constants

None.

php.ini Defaults

None.

Open Issues

  • Decision on function name.
  • Decision on whether it should be in Reflection.

Patches and Tests

A first implementation: https://gist.github.com/krakjoe/5275773

Tests need to be done.

References

Rejected Features

- None.

rfc/instance_counter.1365436896.txt.gz · Last modified: 2017/09/22 13:28 (external edit)