Not all functions are supported by all builds. It depends on your
libpq (The PostgreSQL C client library) version and how libpq is
compiled. If PHP PostgreSQL extensions are missing, then it is because
your libpq version does not support them.
Most PostgreSQL functions accept connection
the first optional parameter. If it is not provided, the last opened
connection is used. If it doesn't exist, functions return FALSE.
PostgreSQL automatically folds all identifiers (e.g. table/column names)
to lower-case values at object creation time and at query time.
To force the use of mixed or upper case identifiers, you must escape
the identifier using double quotes ("").
PostgreSQL does not have special commands for fetching database schema
information (eg. all the tables in the current database). Instead, there
is a standard schema named information_schema in
PostgreSQL 7.4 and above containing
system views with all the necessary information, in an easily
queryable form. See the » PostgreSQL Documentation
for full details.