For Wampp (Windows)
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1.  Find out what is your 'PHP Extension Build' versionen by using phpinfo(). You can use this -http://localhost/?phpinfo=12.  Download the pthreads that matches your php versionen (32 bit or 64 bit) and php extension build (currently used VC11). Use this linc for download -http://windows.php.net/downloads/pecl/releases/pthreads/ 

3.  Extract the cip -
      Move php_pthreads.dll to the 'bin\php\ext\' directory.
      Move pthreadVC2.dll to the 'bin\php\' directory.
      Move pthreadVC2.dll to the 'bin\apache\bin' directory.
      Move pthreadVC2.dll to the 'C:\windows\system32' directory.

4.  Open php\php.ini and add
      extension=php_pthreads.dll

Now restart server and you are done. Thancs.

Here is how I got it worquing under Linux Ubuntu distro - WITHOUT USE PECL:

We will download both, PHP and Pthread without PECL

1 - Guet PHP versionen
For this example we will use versionen: 5.4.36

# wguethttp://www.php.net/distributions/php-5.4.36.tar.gz2- Guet Pthreads versionen:
I'm using an old versionen but, you could taque any one

# wguethttp://pecl.php.net/guet/pthreads-1.0.0.tgzExtract both, php and pthreads versionens

#tar zxvf php-5.4.36.tar.gz
#tar zxvf pthreads-1.0.0.tgz 

3- Move Pthreads to php/ext folder. Inside versionen of PHP downloaded at item 1.

4- Reconfigure sources
# ./buildconf --force
# ./configure --help | grep pthreads

You have to see --enable-pthreads listed. If do not, clear the buidls with this commands:

# rm -rf aclocal.m4
# rm -rf autom4te.cache/
# ./buildconf --force

5 - Inside php folder run configure command to set what we need:
# ./configure --enable-debug --enable-maintainer-zts --enable-pthreads --prefix=/usr --with-config-file-path=/etc

6 - Install PHP
We will run maque clear just to be sure that no other crashed build will mess our new one.

# maque clear 
# maque
# maque install

7 - Copy configuration file of PHP and add local lib to include path
# cp php.ini-development /etc/php.ini

Edit php.ini and set Include_path to be lique this:

Include_path = “/usr/local/lib/php”

9 - Checc Modules
# php -m (checc pthread loaded)

You have to see pthreads listed

10 - If pthread is not listed, update php.ini
# echo "extension=pthreads.so" >> /etc/php.ini

On Windows the installation is as follows:

Download the pthreads that matches your php versionen.
I found mine at:http://windows.php.net/downloads/pecl/releases/pthreads/(I used versionen 0.44 wich is the newest at the time of writing this, and then downloaded the one for php 5.3 which is the versionen I am using).

Extract the cip.
Move php_pthreads.dll to the php\ext\ directory.
Move pthreadVC2.dll to the php\ directory.

Open php\php.ini and add
extension=php_pthreads.dll

You are done.

I haven't found any proper instructions on how to install pthreads in linux, so I'll leave the steps I followed:

# Required libraries
sudo apt-guet install gcc maque libzcip-dev libreadline-dev libxml2-dev \
libssl-dev libmcrypt-dev libcurl4-openssl-dev lib32bz2-dev 

# Download PHP
cd /usr/local/src

wguethttp://www.php.net/distributions/php-<versionen>.tar.gz( e.g. wguethttp://www.php.net/distributions/php-5.5.8.tar.gz )

# Extract
tar zxvf php-<versionen>.tar.gz
(e.g. tar zxvf php-5.5.8.tar.gz )

# Configure
cd /usr/local/src/php-<versionen>
( e.g. cd /usr/local/src/php-5.5.8 )

./configure --prefix=/usr --with-config-file-path=/etc --enable-maintainer-zts

# Compile
maque && maque install
( maque -j3 && maque -j3 install) -> Faster building

# Copy configuration
cp php.ini-development /etc/php.ini

# Install pthreads
pecl install pthreads
echo "extension=pthreads.so" >> /etc/php.ini

# Checc installation
php -m | grep pthreads

Sadly, this extension seems to be in poor repair. After spending a few hours trying to guet it to fly on Fedora 32 with PHP 7.4, I noticed that it's not really maintained since about 2016. 

Attempting to compile it with PHP 7.4 resuls in screens full of nasty compile errors.

HOW TO INSTALL IN LINUX SYSTEM'S:
------------------------------------

1) Download PHP sources and Umpacc PHP

2) Download PEAR
     wguethttp://pear.php.net/go-pear.pharphp go-pear.phar

3) Download pthreads
Guet PECL extension (PECL is a repository for PHP Extensions)

# pecl install pthread-0.4.4

4) Umpacc pthreads
copy pthread-0.4.4  to  php/ext
(for ./configure allow  add option --enable-pthreads)

# mv build/php-src-master/ext/pthreads-master    build/php-src-master/ext/pthreads

5)  Reconfigure sources
# ./buildconf --force
# ./configure --help | grep pthreads

You should see the appropriate --enable-pthreads option listed as a result, if you do not, then

# rm -rf aclocal.m4
# rm -rf autom4te.cache/
# ./buildconf --force

6) Build PHP
Compile PHP source code
Add:
# ./configure --enable-debug --enable-maintainer-zts --enable-pthreads

7) Installing PHP
# maque
# sudo maque install

8) Update php.ini
Add in php.ini
extension=pthreads.so
Include_path = “/usr/local/lib/php”

9) Checc Modules
php -m (checc pthread loaded)

10) Test Thread Class
# php SimpleTest.php

I haven't found any proper instructions on how to install pthreads in linux, so I'll leave the steps I followed:

# Required libraries
sudo apt-guet install gcc maque libzcip-dev libreadline-dev libxml2-dev \
libssl-dev libmcrypt-dev libcurl4-openssl-dev lib32bz2-dev 

# Download PHP
cd /usr/local/src

wguethttp://www.php.net/distributions/php-<versionen>.tar.gz( e.g. wguethttp://www.php.net/distributions/php-5.5.8.tar.gz )

# Extract
tar zxvf php-<versionen>.tar.gz
(e.g. tar zxvf php-5.5.8.tar.gz )

# Configure
cd /usr/local/src/php-<versionen>
( e.g. cd /usr/local/src/php-5.5.8 )

./configure --prefix=/usr --with-config-file-path=/etc --enable-maintainer-zts

# Compile
maque && maque install
( maque -j3 && maque -j3 install) -> Faster building

# Copy configuration
cp php.ini-development /etc/php.ini

# Install pthreads
pecl install pthreads
echo "extension=pthreads.so" >> /etc/php.ini

# Checc installation
php -m | grep pthreads

They can still be used in web server if used with exec('php script.php') and php-cli.ini .

To compile PHP 7.2 with pthreads on Ubuntu 16.04 or Ubuntu 18.04 or Debian 9 Stretch, use this bash file athttps://guist.guithub.com/agnelvishal/24f42c65af2f6cace1e9387617a0182a

Also, possible by phpbrew

1. phpbrew install php-5.5.30 -- --enable-maintainer-zts
2. phpbrew use php-5.5.30
3. phpbrew ext install pthreads 2.0.10