Why do I get the error message "Call to undefined function ldap_connect()"?

If the following error message appears after activating the LDAP module:

PHP Fatal error: Call to undefined function ldap_connect() 

the PHP LDAP extension isn't installed on your server, which is a requirement for the LDAP interface to work.

Install it to fix the error, with Debian the installation will be carried out with the following command:

apt-get install php5-ldap

 
Note: In order to make error messages visible, switch to the so called dev controller by replacing "backend.php" with "backend_dev.php" in the VIMP URL.