How do I install soap extension?

For Windows

1. Find extension=php_soap.dll or extension=soap in php.ini and remove the commenting semicolon at the beginning of the line. Eventually check for soap.ini under the conf.d directory.

2. Restart your server.

For Linux

Ubuntu:

PHP7

Apache

sudo apt-get install php7.0-soap 
sudo systemctl restart apache2

PHP5

sudo apt-get install php-soap
sudo systemctl restart apache2

OpenSuse:

PHP7

Apache

sudo zypper in php7-soap
sudo systemctl restart apache2

Nginx

sudo zypper in php7-soap
sudo systemctl restart nginx

In ubuntu to install php_soap on PHP7 use below commands. Reference

sudo apt-get install php7.0-soap
sudo systemctl restart apache2.service

For older version of php use below command and restart apache.

apt-get install php-soap