Req #61277 [Opn->Nab]: Feature request: Shared Keyword
Edit report at https://bugs.php.net/bug.php?id=61277&edit=1
ID: 61277
Updated by: johannes@php.net
Reported by: thbley at gmail dot com
Summary: Feature request: Shared Keyword
-Status: Open
+Status: Not a bug
Type: Feature/Change Request
Package: *General Issues
Operating System: All
PHP Version: 5.5.0
Block user comment: N
Private report: N
New Comment:
It is a design decision in PHP not to have such global things in PHP itself. Addon modules (you
mentioned apc) can add utilities for this, though.
Some reasons include:
- PHP can be embedded in any application which might add constrains
- correct locking can be hard
- such a feature makes scaling over multiple servers hard
- it messes with copy-on-write
- ...
Previous Comments:
------------------------------------------------------------------------
[2012-03-04 20:29:34] thbley at gmail dot com
update version :-)
------------------------------------------------------------------------
[2012-03-04 20:28:49] thbley at gmail dot com
Description:
------------
Feature request: Shared Keyword
Declaring class properties as shared makes them accessible for all instances of a PHP script
containing the same class name and the same property name.
This functionality allows a shared memory access similar to apc_store() and apc_fetch().
The shared property implies the static property.
Shared propertes can be accessed without needing an instantiation of the class.
If shared is not set for a property, it will be non-shared by default.
Shared properties are accessed through the class name or a class name variable or "self",
and the Scope Resolution Operator "::".
Like any other PHP static variable, shared properties may only be initialized using a literal or
constant; expressions are not allowed.
So while you may initialize a shared property to an integer or array (for instance), you may not
initialize it to another variable, to a function return value, or to an object.
Shared memory limit in php.ini:
shared_memory_limit = 16M
This sets the maximum amount of shared memory in bytes that ALL scripts are allowed to allocate.
To have no shared memory limit, set this directive to -1.
To have an unlimited shared memory limit, set this directive to 0.
When an integer is used, the value is measured in bytes. Shorthand notation may also be used.
Shared variables and properties are initialized only in first call of a function/class and every
time the shared memory is empty.
Scenarios: Caching, performance optimization, counters, progress indicators, parallel queues, etc.
Test script:
---------------
Foo.php: static class property
<?
class Foo
{
shared $cache_shared = "hello"; // public static shared
private shared $_cache_shared = "hello"; // private static shared
protected shared $_cache_shared = "hello"; // protected static shared
shared static $cache_static_shared = "hello"; // invalid, shared implies static
$var1 = "hello"; // public non-static non-shared
}
Foo2.php: static variable
<?
function some_big_calc()
{
shared $a = array();
}
Scenarios:
some_class::$shared_cache = array(...);
some_class::$shared_counter++;
some_class::$shared_progress = 0.3;
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=61277&edit=1
Thread (9 messages)