Doctrine array vs simple_array vs json_array

Question

I am using symfony and doctrine as my ORM.

For available types I have:

• array
• simple_array
• json_array

I am wondering what the difference is between each of them: when do I use one or the other?

Can I have a demonstration for each of them to illustrate the differences?

I already use simple_array in some applications but I find I don't understand formType... (Or maybe I'm not using it well!? )

To illustrate my question, here is an example:

I have an Task that I have to run on specific days So I created TaskEntity with days attribute

Days would be:

$days = array(
    1=>true,
    2=>true,
    3=>true,
    4=>true,
    5=>true,
    6=>false,
    7=>false
);

But I have no idea which of the above types to choose ...

Answer 1

For your problem simple_array is the right way, the right way may also create seven boolean fields.

However here's a little vademecum:

The best way to see how a type works in doctrine is to read the code of the type, this is because there are several details that are taken for granted or are not really explained in the documentation.

So you can go into

/vendor/doctrine/dbal/lib/Doctrine/DBAL/Types/Type.php

find your type and check if its methods work as you want.

Here some details:

simple_array

in /vendor/doctrine/dbal/lib/Doctrine/DBAL/Types/SimpleArrayType.php

return implode(',', $value);

it's just a implode()/explode() of items, stores only the values and it's useful because you can easily query the database.

array

in /vendor/doctrine/dbal/lib/Doctrine/DBAL/Types/ArrayType.php

return serialize($value);

calls PHP to serialize()/unserialize(), it's faster than json_array. Looking at the code I think it also works with objects. Obviously if you see the field as plain text it's uncomprensible.

json_array

in /vendor/doctrine/dbal/lib/Doctrine/DBAL/Types/JsonArrayType.php

return json_encode($value);

it calls json_encode()/json_decode(), if you look in the field you can see a unformatted JSON array but it's more readable than PHP's serialized object and is really more portable (JSON exists everywhere).

June 2018 update

• now there is a complete and more updated documentation here
• json_array is deprecated in favor of json type, it will leverage on new database features for json fields

Answer 2

Another consideration: The most efficient way to represent a small set of true/false values like the ones presented here would be a bitfield.

That way you're only storing one integer instead of a full string. And you avoid the encode/decode overhead.

See https://stackoverflow.com/a/5412214/827254 for a good example.

Answer 3

The best solution for your problem, as stated, would be to use an array mapping of type array or json_array but not simple_array. The reason is that the serialization method of simple_array is just a call to implode(',', $array) and that would retain only the values and not the keys of the array, thus invalid for your situation where you have an associative array.

However, you could also model your $days attribute as a 0-based array (i.e. monday would be zero, tuesday would be 1, etc.). In that case, it would work because the deserializing with explode(',', $serialized); generates a 0-based array with the serialised values.