Description:
------------
pg_connect gives connection resourse to incorrect database.
php.ini default
postgreSQL 9.5 default

using PGSQL_CONNECT_FORCE_NEW help avoid this bug, but too many connections are opened in production

php-v:
PHP 7.0.20-2~ubuntu14.04.1+deb.sury.org+1 (cli) (built: Jun 14 2017 05:55:23) ( NTS )

Test script:
---------------
<?php

try {
    $count = 0;
    while ($count < 1000) {
        $names = ['test1', 'test2', 'test3', 'test4'];
        $name = $names[mt_rand(0,3)];

        $resource = pg_connect("user=postgres dbname=$name host=db-host port=5432");
        if (is_resource($resource) && pg_dbname($resource) !==  $name) {
            /**
             * got it !!!
             */
            echo "count $count \n";
            echo "resource $resource\n";
            echo "is_resource ".is_resource($resource)."\n";
            echo "pg_dbname " .pg_dbname($resource). "\n";
            echo "name $name\n";
            die(1);
        }
        ++$count;
        usleep(1000);
    }
} catch (Exception $e) {
    echo $e . "\n";
}

Expected result:
----------------
empty output if everything correctly, or exception in case couldn't connect.


Actual result:
--------------
count 26
resource Resource id #23
is_resource 1
pg_dbname test3
name test2

that mean asking for connection to test2, but it gives test3