LDAP connexion issue

Hello,

I'm trying to configure ldap connexion on my OCS server.
I configured CONEX_LDAP_SERVEUR / CONEX_ROOT_DN / CONEX_ROOT_PW / CONEX_LDAP_PORT / CONEX_DN_BASE_LDAP /  CONEX_LOGIN_FIELD / CONEX_LDAP_PROTOCOL_VERSION on the server.
I also modified /usr/share/ocsinventory-reports/ocsreports/backend/identity/identity.php and /usr/share/ocsinventory-reports/ocsreports/backend/AUTH/auth.php files, and restarted HTTPD

The issue is that I try to login on OCS console I get HTTP 500 errror.
 

On the HTTPD error log I get : [:error] [pid 29310] [client 10.210.110.17:55688] PHP Fatal error:  Call to undefined function ldap_connect() in /usr/share/ocsinventory-reports/ocsreports/backend/AUTH/methode/ldap.php on line 124, referer: http://ocsserver/ocsreports/index.php

Telnet port 389 to LDAP server is OK.

I found few post on forum and github with this issue but no solution.

Thanks and regards