admin/environment/php extension/soap
From MoodleDocs
Install Soap module for PHP 5
Debian:
- apt-get install php5-soap
Centos:
Download and install soap
yum install php-soap
For Windows 1) Locate php.ini eg For xampp. C:/xampp/php/php.ini 2) Search for the string inside the quotes - ";extension=php_soap.dll" 3) Remove the semi colon, save the file and restart apache.