Mysql_connect() and all Mysql functions fail under PHP

Hello people, I got to run Apache, Mysql and PHP on linux. I checked some 'test.php' page using only echo $vars and it works ok, variable displaying and PHP script executing ok. I also checked Mysql , creating a tiny database (terminal mode) and also it performs ok. BUT when I try to execute any Mysql functions (the first being Mysql_connect(user,db,password), it returns HTM page saying 'trying to use some unsopported function mysql_connect()...'. I checked with other Mysql functions and all of them returns same error. Help, I checked PHP.INI and HTTP.CONF files , all appears to be ok. Miguel