Script for reproducing bug:

while(!($con=@pg_pconnect("dbname=web")))
{
   sleep(1);
}

The system must be under heavy load for bug to become apparent.

Suggested correction in ext/pgsql/pgsql.c (added lines are marked with ***):

if (pgsql==NULL || PQstatus(pgsql)==CONNECTION_BAD) {
***   if(pgsql) {
***      PQfinish(pgsql);
***      pgsql=0;
***   }
    php_error(E_WARNING,"Unable to connect to PostgreSQL server:  %s",PQerrorMessage(pgsql));
    efree(hashed_details);
    RETURN_FALSE;
}