Re: [PHP-DEV] Needs some clarification on static zend_string vs zend_new_interned_string (php internals).

Hi David,

On Wed, Sep 16, 2026 at 4:16 PM David Maye Kitenge <[email protected]>
wrote:

> Hello everyone,
>
> My name is David. I'm working on the refactoring of a PHP extension from
> "Zephir" language to a cleaner C language output.
>
> I came across the fact that the extension uses a lot of "static"
> zend_string.  No I want to convert those static zend_string  into the
> intern string.
>
> From what I read today based on PHP internal book website and PHP Source
> online, calling a Zen's new interest string function create a string whose
> value is registered into a hash table.  And then on a request in it this or
> that send interned string is then retrieved from the hash table instead of
> creating a new Zen string. Apart from the fact that every every news and
> intern strings have an immutable ref count.
>
> My doubt is the following:
>
> * Does ref counting increments/decrements when you create a Zend string
> using the static keyword?
>

static applies to the C variable, not the string’s reference-counting
behaviour. A string held in static zend_string *s is still normally
refcounted unless it is interned.


> * Assigning a new zend_string as interned zend_string, when the flag
> "IS_Interned_STRING" (if I remember correctly), the string is kinda garbage
> collected? (Do I need to free the string)?
>

An actually interned string is managed by Zend/OPcache. The string
copy/release helpers leave its refcount unchanged, and you should not free
it directly.

To convert an existing string you own:
`s = zend_new_interned_string(s);`
Store the returned pointer, and the function will release the original
string and return an existing interned one. Do not separately release the
old pointer.
But, you should still use `zend_string_release(s)` when finished with your
owned reference. It is a no-op for interned strings, but handles
non-interned results, which these APIs can return with OPcache during a
request.

For fixed extension strings needed across requests, initialize them during
normal module startup (MINIT):
`s = zend_string_init_interned("example", sizeof("example") - 1, true);`

Strings interned during a request are not necessarily permanent; storing
their pointer in a static variable does not extend their lifetime.

Regards,
-- 
Alex

>