Re: XPath Search

[Nigel S. <nig...@us...>]

I've narrowed the problem down.  When I search through keywords in the =
xml file (each component has one keyword tag with multiple words) it =
works fine using:
$components=3D$xPath->match("//component[contains(keyword,'string')]");
but when I search through features (each component has multiple =
features) using:
$components=3D$xPath->match("//component[contains(feature,'string')]");
I get an empty array.

Do I have to do something different if there are multiple tags such as =
feature?

Worked it out.  When you search for =
//component[contains(feature,'string')], then it first of all evaluates =
//component to get a list of context nodes, which will be something =
like:

XPathSet:Array
(
    [0] =3D> /product[1]/component[1]
    [1] =3D> /product[1]/component[6]
)


Then it filters the list based on the predicate, which is the =
contains(feature,'string') bit.  But to do this, it needs to evaluate =
the "feature" for each of the context nodes.  But for the first context =
node this returns something like:

Array
(
    [0] =3D> /product[1]/component[1]/feature[1]
    [1] =3D> /product[1]/component[1]/feature[2]
    [2] =3D> /product[1]/component[1]/feature[3]
    [3] =3D> /product[1]/component[1]/feature[4]
)


So the LHS is an array, and the RHS is a string.  According to =
http://www.w3.org/TR/xpath#function-string, the contains function will =
convert the LHS to a string by "A node-set is converted to a string by =
returning the string-value of the node in the node-set that is first in =
document order. If the node-set is empty, an empty string is returned.". =
 And thus it will take the text part of =
/product[1]/component[1]/feature[1], and ignore the rest.

This explains why it works for the keyword, as you only have one =
keyword.

Instead of finding all components, and then filtering the list, instead =
we should find all features, and then go back up a level to get their =
owning components.  So we do:

//feature[contains(.,'search string')]/..

Nigel