ZEND PHP 5 Certification STUDY GUIDE

196 ” XML and Web Services
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If a file with the same path already exists, a call to asXML() will overwrite it without
warning (provided that the user account under which PHP is running has the proper
permissions).
While SimpleXML provides the functionality for adding children and attributes, it
does not provide the means to remove them. It is possible to remove child elements,
though, using the following method.
$library->book[0] = NULL;
This only removes child elements and their attributes, however. It will not remove
attributes from the element at the book level. Thus, the isbn attribute remains. You
may set this attribute to NULL, but doing will only cause it to become empty and will
not actually remove it. To effectively remove children and attributes, you must export
your SimpleXMLElement to DOM (explained later in this chapter), where this more
powerful functionality is possible.
Working With Namespaces
The use of XML namespaces allows a provider to associate certain element and attribute
names with namespaces identified by URIs. This qualifies the elements and
attributes, avoiding any potential naming conflicts when two elements of the same
name exist yet contain different types of data.
The library.xml document used thus far does not contain any namespaces, but
suppose it did. For the purpose of example, it might look something like this:
Fahrenheit 451
Ray Bradbury
Del Rey
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