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Introduction

Introduction -- Using XPath

Why XPath support?

The XPath support was introduced to provide an access to the result set after doing the SQL query. This allows further proccessing of the result set without quering the database again.

XPath is a W3-Standard and for further information about that, ask your preferred XSL/XML book, or http://www.w3.org/.

Passing an XPath expression

XML_sql2xml provides two functions for querying the result set: getXpathValue() and getXpathChildValues(). Both expect a XPath query and return the result as string or array.

Example 68-1. getXpathValue

<?php
include_once("XML/sql2xml.php");
$sql2xmlclass = new xml_sql2xml("mysql://username:password@localhost/xmltest");
$sql2xmlclass->add("select * from bands");
$xmlstring  = $sql2xmlclass->getXpathValue("/root/result/row[id = '2']/name");
?>

$xmlstring contains: 

$xmlstring = 'Only Stupids'

Example 68-2. getXpathChildValues

<?php
include_once("XML/sql2xml.php");
$sql2xmlclass = new xml_sql2xml("mysql://username:password@localhost/xmltest");
$sql2xmlclass->add("select * from bands");
$xmlstring  = $sql2xmlclass->getXpathChildValues("/root/result/row[id = '2']");
?>

$xmlstring contains: 

Array
(
    [] => 
    [id] => 2
    [name] => Only Stupids
    [birth_year] => 1997
    [birth_place] => New York
    [genre] => Hip Hop
)

Mixing SQL and XPath query

You can insert an XPath query into an SQL query. In the example, first a SQL query is done, in the second a SQL query done again - but the parameter for bandsID is taken from the XPath expression in the curly braces. This expression is processed on the result set of the first SQL query.

Example 68-3. Mixed query

<?php
include_once("XML/sql2xml.php");
$sql2xmlclass = new xml_sql2xml("mysql://username:password@localhost/xmltest");
$sql2xmlclass->add("select * from bands");
$sql2xmlclass->add("select * from albums where bandsID = {/root/result/row[name = 'The Blabbers']/id}");
$xmlstring = $sql2xmlclass->getxml();
?>
$xmlstring = '

<?xml version="1.0"?>
    <root>
        <result>
            <row>
                <id>1</id>
                <name>The Blabbers</name>
                <birth_year>1998</birth_year>
                <birth_place>London</birth_place>
                <genre>Rock'n'Roll</genre>
            </row>
            <row>
                <id>2</id>
                <name>Only Stupids</name>
                <birth_year>1997</birth_year>
                <birth_place>New York</birth_place>
                <genre>Hip Hop</genre>
            </row>
        </result>
        <result>
            <row>
                <id>1</id>
                <bandsID>1</bandsID>
                <title>BlaBla</title>
                <year>1998</year>
                <comment>Their first one</comment>
            </row>
            <row>
                <id>2</id>
                <bandsID>1</bandsID>
                <title>More Talks</title>
                <year>2000</year>
                <comment>The second one</comment>
            </row>
        </result>
    </root>
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