MasterPress 1.3.1 is a compatibility release for PHP 8 and WordPress 5.7. It still remains backwards compatible with older PHP versions.
MEOW_Field :: prop( String $name = null, String $value (optional) = null )
Either get or set a named property associated with this field type, or retrieve an associative array of all properties and values if the $name argument is not provided. A property in this case is not a standard PHP object property, but rather a meta property that further clarifies the value of this field. Only the richer field types support properties on the value of the field, with the most notable being Image type which stores alt and title attributes as properties, and the Video field type which stores the properties retrieved from the YouTube or Vimeo APIs as properties.