parallel requires a build of PHP with ZTS (Zend Thread Safety) enabled (--enable-zts, or on non-Windows systems prior to PHP 8.0.0, --enable-maintainer-zts)


Zend Thread Safety cannot be enabled post build; it is a build time configuration option.

parallel should build anywhere there is a working Posix Threads header (pthread.h) and ZTS build of PHP, including Windows (using the pthread-w32 project from redhat).


parallel releases are hosted by PECL and the source code by » github, the easiest route to installation is the normal PECL route: »

Windows users can download prebuilt release binaries from the » PECL website.


Windows users need to take the additional step of adding pthreadVC2.dll (distributed with Windows releases) to their PATH.

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User Contributed Notes 3 notes

1 year ago
As it seems, the last compiled Windows version is for PHP 7.4 which PHP 8.x refuses to load as extension. In his GitHub repository the author of the parallels extension wrote on August 2021 that the project is "probably a dead end" and the project hasn't been updated since 2 years.
1 year ago
Version 1.2.0, released on October 24, 2022, supports PHP 8.0.0.
andre at webtechnik dot ch
3 years ago
On Windows Systems:

- Install PHP TS (Thread Safe)
- Download Extension from PECL (PHP-Version, Thread Safe (TS), Compiler - Version (VC15, VC16), Architecture must match)
- Copy extension to folder: <your php dir>/ext/php_parallel.dll
- Copy app to folder: <your php dir>/pthreadVC2.dll (It is important to copy pthreadVC2.dll not into the ext folder!)
- add pthreadVC2.dll to windows system environment path
- add in php.ini the line extension=parallel to load the extension
- restart

Try on console: php -v

If there are no errors, everything works and you can try the examples
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