Xpath is an usefull language to browse a XML file easily. I will explain you the basics of this tool, with a PHP environment (From PHP 5.2.0). If you want a complete documentation, you can read this article of w3schools.com.
Open a XML file
Let’s make a loop on a XML nodes list :
$xml = new SimpleXMLElement('XML_PATH_FILE', Null, True);
$nodes = $xml->xpath('YOU XPATH REQUEST');
foreach($nodes as $node) {
$node->getName() // Return node's name
$node->childName // Return childName's value (Case sensitive !)
}
XPath Requests Syntax
In the previous example, you probably saw a line we need to explain :
$nodes = $xml->xpath('YOU XPATH REQUEST');
We will learn how to write request for Xpath
Expressions
| Expression | Explaination |
|---|---|
| nodename | Every nodes named “nodename” |
| / | Attached on document’s root |
| // | Everywhere on the document |
| . | Current node |
| .. | Parent node |
| @ | To select an attribute |
Some examples :
- /root/elements/element : Every nodes named “element” which are child of “elements”, which is a child of “root”
- //elements/element : Every nodes named “element” which are child of “elements”, everywhere in the docuement.
- //elements/.. : Select parent node of every “elements” nodes
- //@myattribute : Select every attributes named “myattribute” everywhere in document
Predicates
| Predicate | Explaination |
|---|---|
| /elements/element[1] | Select first “element” of “elements” |
| /elements/element[last()] | Select last “element” of “elements” |
| /elements/element[last()-1] | Select penultimate “element” of elements” |
| /elements/element[position()<3] | Select the first two “element” of “elements” |
| //element[@myattribute] | Select “element” which have an attribute named “myattribute” |
| //element[@myattribute=’myvalue’] | Select “element” which have an attribute named “myattribute” which have the value “myvalue” |
| /elements/element[subelement>10] | Select “element” which have a “subelement” with a value greater than 10 and child of “elements” |
| /elements/element[subelement>10]/subsubelement | Select “subsubelement” of “element” which have a “subelement” with a value greater than 10 and child of “elements” |
Search unknown elements
| Syntax | Explaination |
|---|---|
| * | Any node |
| @* | Any attribute |
| node() | Every nodes |
Some examples !
- /elements/* : Every children of node named “elements”
- //subelement[@*] : Every attributes of nodes named “subelement” everywhere in the document
You now know the basics of the XPath language which allow you to browse XML files easily. If you want to learn more about this language, you can find an article on the W3C website.
XPath and PHP
Imagine we did our xpath request, and we are in our foreach loop. We have an object in our variable $node, we can manipulate it.
| Syntax | Explaination |
|---|---|
| $node->getName() | Get node’s name (Usefull if your request is like “/elements/*”) |
| $node->childName | Get child’s value named “childName” (Case sensitive!) |
To realize this new knowledge, nothing better than practice 😉