====== Filter class ======

The filter class is used as an easy and high performance way of retrieving Datarecords.

A filter is constructed by naming which class we want to filter

<code php>
$filter = new Filter('User');
</code>

Then one or more conditions can be added:

<code php>
$filter->addCondition(new ConditionMatch('lastname', 'sahl'));
</code>

And at last the filter is executed which will return a [[collection_class|Collection]] with the results.

<code php>
$datacollection = $filter->execute();
</code>

===== Conditions =====

The following conditions are available:

<code php>
new ConditionAND($condition1, $condition2);
// Return objects for which both conditions are true.

new ConditionGreater($field, $value);
// Return objects where the content of $field are greater than $value.

new ConditionGreaterEqual($field, $value);
// Return objects where the content of $field are greater or equal than $value.

new ConditionInFilter($field, $filter);
// Return objects where the content of $field are present in the filter $filter.

new ConditionLesser($field, $value);
// Return objects where the content of $field are lesser than $value.

new ConditionLesserEqual($field, $value);
// Return objects where the content of $field are lesser or equal than $value.

new ConditionLike($field, $value);
// Return objects where the content of $field contains part of $value.

new ConditionMatch($field, $value);
// Return objects where the content of $field is exactly $value.

new ConditionNOT($condition);
// Return all objects which isn't matched by $condition.

new ConditionOR($condition1, $condition2);
// Return objects where one of the conditions is true.

new ConditionOneOf($field, $values);
// Return objects where the content of $field is one of the supplied $values.
</code>

Not all conditions work on all field types.

===== Serializing filters =====

Filters can be serialized as a JSON string, so they can be stored in databases or passed through forms. 

<code php>
$json = $filter->toJSON();
</code>

And they can be reconstructed just as easy.

<code php>
$filter = Filter::getFilterFromJSON($json);
</code>