Question: Starting with version 5.3, PHP supports [late binding](http://en.wikipedia.org/wiki/Name_binding#Late_static) for static methods. While it's an undoubtedly useful feature, there are only several cases where its use is really necessary (e.g. the Active Record pattern). 

Consider these examples:

**1. Convenience constructors (`::create()`)**

```
class SimpleObject
{
    public function __construct() { /* ... */ }

    public static function create()
    {
        return new static; // or: return new self;
    }
}

```

If this class may be extended (however, it's not extended by any class in the same package), should late static binding be used just to make extending it easier (without having to rewrite the `::create()` method, and, more importantly, without having to remember to do that)?

*Note: this idiom is used to work around the impossibility to call methods on just constructed objects: `new SimpleObject()->doStuff()` is invalid in PHP.* 

---

**2. Class constants**

```
class TagMatcher
{
    const TAG_PATTERN = '/\<([a-z\-]+?)\>/i';

    private $subject;

    public function construct($subject) { $this->subject = $subject; }

    public function getAllTags()
    {
        $pattern = static::TAG_PATTERN;
        preg_match_all($pattern, $this->subject);
        return $pattern[1];
    }
}

```

The reason to use `static::` in this example is similar to the previous one. It's used just because this class can be made to match differently formed tags just by extending it and overriding the constant.

---

So, to wrap it all up, are these uses (and similar ones) of late static binding are an overkill? Is there any noticeable performance hit? Also, does frequent use of late binding reduce the overall performance boost given by opcode caches?

Answer: 
static methods (early- or late-bound) create tight coupling and (thus) reduce testability. you can create large programs in PHP without using more than a few static calls. for me, late static methods are a non-feature.

**edit** to answer Marco Demaio's question, *how do static method reduce testability?*

i'm sorry if this is all obvious to you, static members (both data and methods) *are* useful and do no harm if used responsibly, i was alluding to their prevalent misuse.

say you have a web application that uses an SQL database. your business objects may retrieve data using a static interface or through polymorphism. either

```
class MyBusinessObject
extends...
{
  public function doThisOrThat(...)
  {
    $results = db::query('sql string...');
    ...
  }
}

```

or

```
class MyBusinessObject
extends...
{
  public function __construct(dbconn $db)
  {
    $this->db = $db;
  }
  private $db;
  public function doThisOrThat(...)
  {
    $results = $this->db->query('sql string...');
    ...
  }
}

```

the latter is easier to test (as in: i want to test that the sql string constructed from such-and-such inputs is such-and-such) because it's easier to create another implementation of the `dbconn` interface than it is to change the meaning of `db::`. why you'd want either? because you don't need a real database to test the sql-composing behavior, and in fact it's easier to test for *without* a real database. also, it's easier to stub out the sql consumer if your tests are concerned with another aspect of the CUT (Code Under Test).

testing always implies lying to the tested code about its collaborators, and abstaining from static interfaces (the "doublecolon" or "quadridot") means the lie need not be a massive surgery, which is a plus, since the farther the tested code is from the production code, the less meaningful the test results are.
Where I find a need to use late static binding is to allow mocking of static methods for unit testing with PHPUnit. The problem I have is that I don't like changing code strictly to allow mocking, but I can get over that.

To answer your question, however, I would bet that whatever performance cost this carries, it will pale in comparison to most program runtimes. In other words, it won't make a noticeable difference.