<?php
$conn=pg_connect("connection string");
$conn1=pg_connect("connection string");
echo $conn."<br>";  // output 1
echo $conn1."<br>";  // output 1
pg_close($conn);
pg_close($conn1); // results in invalid resource ID error
?>

looking at the code I can see that if you try to open two db connections, with the same connection string, only one
really get opened, to the second one instead is assigned the same resource ID of the first and zend_list_addref function is called for the resource. If you close the first connection, it really get closed taking no care of the
number of references to the resource.