What is it? –w3c standard for… Navigating through an XML document Filtering & finding information –Includes… Expressions for navigating to parts of an XML document The standard includes functions (e.g. for string & date manipulation)‏ Also used in XSLT for xml transformation

What are they? (or sets of nodes) from an XML document –They consist of… A path to the nodes/node sets A predicate (optional)‏ Syntax –Without a predicate: Nodenames, separated by a forward slash (/)‏ –Predicates: Predicates are placed inside [ ]

P Anabela Domingues P 2004 M Ann Devon U student.xml Root nodeChild of root node Children of student

What would be the path expression to navigate to the startYear node? What would be the path expression to select the startYear node where the startYear = 2002? ‘/students/student/startYear’ ‘/students/student/startYear[. = “2002”]’ --- OR --- ‘/students/student[startYear = “2002”]/startYear’ has more details on & examples of path expressions

 What would be the path expression to select student nodes where the startYear = 2002 and the studyTypeIdD= U? '/students/student[startYear=2003][studyTypeID = "U"]' has more details on & examples of path expressions

The aim of the example used in the following slides is to list data in a XHTML table for all students who started at University in 2002 e.g. Fiona Murray M … … Ann Devon M Name Student Code

Steps involved in this example: 1.Create an instance of a simpleXML class by loading the XML file 2.Construct the query expression 3.Call the XPath method to execute the query 4.Loop through the result set

// Create a new simplexml instance loading xml file $studentsXML = simplexml_load_file('student.xml'); // Construct an XPath expression, // including a predicate in this instance. $qry = '/students/student[startYear = "2002"] '; // call the simplexml xpath method $students = $studentsXML->xpath($qry);

// iterate through the students returned by the xpath query foreach ($students as $student) { } echo " {$student->studentCode} \n"; echo " {$student->forename} "; echo "{$student->surname} \n"; echo " \n"; echo " {$student->studentCode} \n"; echo " {$student->forename} "; echo "{$student->surname} \n"; echo " \n"; echo " Student Code Name \n"; echo " \n";

 XPath is a w3c standard for  Navigating through an XML document  Filtering & finding information  Path expressions navigate to a particular node or node-set and they may include predicates

- Xpath tutorial - XPath in 5 paragraphs! - w3schools XPath tutorial & reference *