postgresqlhstoreをphp配列に変換します

構文は次のようになると思います：

$pdo = new PDO( /*connection string*/ );
// h is the hstore column.
$stmt = $pdo->query( "SELECT (each(h)).key, (each(h)).value FROM <table name>" );
$output = array();
foreach( $stmt->fetchAll( PDO::FETCH_NUM ) as $row )
{
   // $row[ 0 ] is the key, $row[ 1 ] is the value.
   $output[ $row[ 0 ] ] = $row[ 1 ];
}