Use PHP's native json_encode, like this:

<?php
$arr = array(
    array(
        "region" => "valore",
        "price" => "valore2"
    ),
    array(
        "region" => "valore",
        "price" => "valore2"
    ),
    array(
        "region" => "valore",
        "price" => "valore2"
    )
);

echo json_encode($arr);
?>

Update: To answer your question in the comment. You do it like this:

$named_array = array(
    "nome_array" => array(
        array(
            "foo" => "bar"
        ),
        array(
            "foo" => "baz"
        )
    )
);
echo json_encode($named_array);