Filters

JSON Schema specification contains a lot of keywords to validate data, but most of them are only for range check (like minimum, maximum, minLength, …). So, what happens if you want to check if something exists in a database? Well, there cannot be such thing in json schema because it requires a lot of information (hostname, username, pass, query, …) and it will be a pain to debug or reuse the schema, not to mention about security concerns.

That’s why we created a way to add PHP logic as filters in json schema, by adding a new non-standard keyword named $filters.

Custom filters can be expensive, so please note that $filters is the last property checked.

General structure

In a json schema document, $filters can be: a string, an object or an array of strings and objects.

$filters keyword support is enabled by default, to disable it use Opis\JsonSchema\Validator::filtersSupport(false).

If your filter doesn’t need any arguments (besides the value that is validated) you can use it like a string.

{
  "$filters": "myFilter"
}

If you need to send some arguments to filter use an object, where $func keyword holds the filter name and $vars keyword (optional) holds a map of arguments (see more info about $vars).

{
  "$filters": {
    "$func": "myFilter",
    "$vars": {
      "arg-name-1": 2,
      "arg-other": "something else" 
    }
  }
}

You can even use multiple filters by creating an array.

{
  "$filters": [
    "firstFilter", 
    {
      "$func": "secondFilter",
      "$vars": {
        "var1": 1,
        "var2": "value"
      }
    },
    "lastFilter"
  ]
}

Please note that if you use an array of filters and one filter doesn’t validate the data, the remaining filters will not be called.