how can I install pspell in php5/ubuntu?

For those using PHP 7.2 / Ubuntu 18.10, here is what I did to get PSPELL working:

sudo apt-get install php5-pspell
sudo apt-get install php-pspell
sudo apt-get install aspell-en
sudo apt-get install aspell-fr
sudo apt-get install aspell-de
sudo apt-get install aspell-es
sudo service apache2 restart 

I use multiple languages, so included some of them in the example above. I believe EN is included by default.

just do

sudo apt-get install libpspell-dev 
sudo apt-get install php5-pspell
sudo apt-get install aspell-en

then restart your apache2 server with the following command

sudo service apache2 restart 

it will be added automatically to your php.ini

you can try this example