Código PHP:
$host = "localhost:/1";
$username = "1";
$password = "1";
$conexion=ibase_pconnect ($host, $username, $password) or die ("Error en la conexion a la Base de Datos Firebird");
$host2 = "localhost:/2";
$username2 = "2";
$password2 = "2";
$conexion2=ibase_pconnect ($host2, $username2, $password2) or die ("Error en la conexion a la Base de Datos Firebird");
$host3 = "localhost:/etc...";
$username3 = "etc..";
$password3 = "tec..";
$conexion3=ibase_pconnect ($host, $username, $password) or die ("Error en la conexion a la Base de Datos Firebird");