# Using the required Argument

Fields may be linked/required/folded according to a/multiple parent value(s). This is accomplished by appending a required argument to the field. Required can be very powerful, but due to the complexity requires some careful consideration when using.

# Example Config

To link a field's visibility to the value of another:

array(
    'required' => array( 'LINKED_FIELD_ID', 'OPERATION', 'VALUE' )
)
Key Description
LINKED_FIELD_ID Field ID that will affect the visibility of this field
OPERATION Comparison operation to perform
VALUE Value is the value to compare against for visibility

You can also link a field with multiple "parent" required values. If all of these conditions are not met, this field will not be visible and the field CSS will not be used. An example is as follows:

array(
    'required' => array( 
        array( 'LINKED_FIELD_ID_1', 'OPERATION_1', 'VALUE_1' ), 
        array( 'LINKED_FIELD_ID_2', 'OPERATION_2', 'VALUE_2' ) 
    )
)

# Operations Available

To attempt to support the various possibilities, a number of options have been coded. These operations have been found to support the majority of needs.

Operation Test Equivalent
= $a = $b
equals $a = $b
!= $a != $b
not $a != $b
> $a > $b
greater $a > $b
is_larger $a > $b
>= $a >= $b
greater_equal $a >= $b
is_larger_equal $a >= $b
< $a < $b
less $a < $b
is_smaller $a < $b
<= $a <= $b
less_equal $a <= $b
is_smaller_equal $a <= $b
contains ( strpos( $a, $b ) !== false )
doesnt_contain ( strpos($a, $b) === false )
not_contain ( strpos($a, $b) === false )
is_empty_or if ( empty( $value1 )
not_empty_and if ( !empty( $value1 ) && $value1 != $value2 )

# Nesting

As of Redux 3.2.0 nested requireds fully function. If any parent is hidden or doesn't match the value, all children are hidden and all CSS output from those children is hidden as well.

# CSS Output

CSS output to both the head and compiler is removed from each field if the required value(s) is/are not met. You can, however, override this on a per field basis by setting 'force_output' => true for each field you want CSS to still be output with. This way you can nest a field under another, and still have it output to the dynamic CSS.

TIP

The CSS output will always be visible if items are within a section field unless that specific field has the required value set to the required parent as well.