SwatML for this demo:
<?xml version="1.0" standalone="no"?>
<!DOCTYPE swatml SYSTEM "http://swat.silverorange.com/swatml1.dtd">
<swatml>
<widget class="SwatForm" id="my_form">
<property name="action">index.php?demo=FileEntry</property>
<widget class="SwatFormField">
<property name="title" type="string">Entry</property>
<widget class="SwatFileEntry" id="file_entry">
<property name="accept_mime_types[]">image/gif</property>
<property name="accept_mime_types[]">image/jpeg</property>
<property name="accept_mime_types[]">image/png</property>
<property name="required" type="boolean">true</property>
</widget>
</widget>
<widget class="SwatFooterFormField">
<widget class="SwatButton">
<property name="title" type="string">Upload</property>
</widget>
</widget>
</widget>
</swatml>