APORTE: clase conectar php con postgres, se reciben sugerencias para mejorarla

[eulloa]

Bueno, allá va la primera. Según el mismo manual
Note: In order to maintain backward compatibility with PHP 4, PHP 5 will still accept the use of the keyword var in property declarations instead of (or in addition to) public, protected, or private. However, var is no longer required. In versions of PHP from 5.0 to 5.1.3, the use of var was considered deprecated and would issue an E_STRICT warning, but since PHP 5.1.3 it is no longer deprecated and does not issue the warning.
If you declare a property using var instead of one of public, protected, or private, then PHP 5 will treat the property as if it had been declared as public.
Así que ya q usas php5, utiliza modificadores de acceso
Otra: No veo por ningún lado donde se arma el query