Package.xml file for permission set in salesforce

Sample package.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
    <types>
        <members>Testing</members>
        <name>PermissionSet</name>
    </types>
    <version>36.0</version>

</Package>

Note: Place all permission sets by adding new row as members.
For eample: Testing is api name of permission set.