File form field type
From Joomla! Documentation
Provides an input field for files
- type (mandatory) must be file.
- name (mandatory) is the unique name of the field.
- label (mandatory) (translatable) is the descriptive title of the field.
- description (optional) (translatable) is text that will be shown as a tooltip when the user moves the mouse over the drop-down box.
- default (optional) (not translatable) is the default value, but doesn't mean much for a file.
- size (optional) is the width of the file box in characters.
- accept (optional) Tells the browser what MIME types your form will allow to be uploaded.
- class (optional) is a CSS class name for the HTML form field.
- labelclass (optional) adds a CSS class for form field's label; for Joomla 2.5.4+
- disabled (optional) HTML equivalent attribute
- required (optional) For Joomla form validating it to be filled in
- validate (optional) Whether to Joomla validate the field according to rules
- showon (optional) Allows you to hide the field based on the value(s) of another field; for Joomla 3.2.4+
Note: When using the file input type you should always add the attribute enctype="multipart/form-data" to your form tag. Otherwise, the uploaded files will not be attached correctly. Note 2: You can put a soft limit file size by adding a hidden field with name="MAX_FILE_SIZE" and value the maximum allowed bytes which is handled by php, but you must also handle it in your code with or without it.
Example XML field definition:
<field name="myfilevalue" type="file" label="Enter some text" description="Choose an image from your computer with maximum 100KB" size="10" accept="image/*" />