Description:
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Multiple database connections opened via pg_connect are not being garage collected & closed. 

Test script:
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<?php

$dbLink1 = pg_connect( "host=localhost port=5432 dbname=development", PGSQL_CONNECT_FORCE_NEW );
pg_query($dbLink1, 'select 1; /*FIRST*/');

$dbLink2 = pg_connect( "host=localhost port=5432 dbname=development", PGSQL_CONNECT_FORCE_NEW );
pg_query($dbLink2, 'select 1; /*SECOND*/');

/*closing first link*/
pg_close($dbLink1);

$dbLink2 = pg_connect( "host=localhost port=5432 dbname=development", PGSQL_CONNECT_FORCE_NEW );
pg_query($dbLink2, 'select 1; /*THIRD*/');

/*2nd 3rd connection remain idle on the database connection as long as the scripts is alive, the 2nd connection overridden by $dbLink2 should be automatically destroyed*/

sleep(200); 

?>

Expected result:
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Only one connection referenced by $dbLink2 should be open on the database. The problem doesn't appear on earlier versions of php 5, works fine in php 5.5, 5.6 and the database correctly reports only 1 connection idle

Actual result:
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2 open idle connections reported on the database on any PHP 7.X version, 

#1. idle connection for the query of select 1; /*SECOND*/
#2. idle connection for the query of select 1; /*THIRD*/