XML parsing error: undefined entity - special characters

Question

Why is there an error displaying XML on some special characters, and some are okay?

For example, an error will be generated below,

<?xml version="1.0" standalone="yes"?>
<Customers>
    <Customer>
        <Name>L&ouml;ic</Name>
    </Customer>
</Customers>

but it normal,

<?xml version="1.0" standalone="yes"?>
<Customers>
    <Customer>
        <Name>&amp;</Name>
    </Customer>
</Customers>

I am converting a special character through php - htmlentities('Löic',ENT_QUOTES). By the way

How can I get around this?

Thank.

EDIT:

I found that it works fine if I use a numeric character like Lóic

now I have to find how to use php to convert special characters to numeric characters!

Answer 1

The XML specification, there are five objects - &, <, >, 'and"

, DTD HTML.

HTML XML.

, , , ( :

• , UTF-8
• , , UTF-8
• , , UTF-8
• , , HTTP , UTF-8 ( XML UTF-8 , - )

)

Answer 2

, DTD.