I’ve prepared something very useful for you today. Setting a default value. For any relational databases it is very common practice to set some default value if user doesn’t specify any value. For example if we have boolean field and we don’t set default value, in the records we will find one of those values: true, false, null. And there is a question – what does null mean for that column? Is it the same thing as false? Or should we handle nulls in some other way? If you don’t mean to have 3 types of values you should set the default value. This practice is also useful when in the beginning this field will always have the same value an it will be changed any time later.
Database is just one of the layers. When you are using a framework like Symfony 2 you have other layer which is ORM. In this particular case it is Doctrine 2. You should also set the default value there. You can do it by adding a row

"default" = 0

in options argument when declaring an ORM column. For example, it can look like this:

@ORM\Column(
    name="foo",
    type="decimal",
    precision=7,
    scale=2,
    options={"default" = 0}
)