Example 7: XSLT Transformation

Convert an XML document into HTML by applying an XSLT stylesheet

🎯 What does this example cover?

XSLT (eXtensible Stylesheet Language Transformations) es un lenguaje que describe cómo transformar un documento XML en otro formato: HTML, texto plano o incluso otro XML. Este ejemplo aplica de verdad una hoja de estilo XSLT sobre el listado de libros usando la extensión XSLTProcessor de PHP, generando una tabla HTML. Puedes elegir el orden de los resultados, que se controla mediante un parámetro XSLT.

Configure the transformation

ℹ️ Source XML 
<?xml version="1.0" encoding="UTF-8"?>
<biblioteca>
    <libro>
        <titulo>El Quijote</titulo>
        <autor>Miguel de Cervantes</autor>
        <anio>1605</anio>
    </libro>
    <libro>
        <titulo>Cien anios de soledad</titulo>
        <autor>Gabriel Garcia Marquez</autor>
        <anio>1967</anio>
    </libro>
    <libro>
        <titulo>Orgullo y prejuicio</titulo>
        <autor>Jane Austen</autor>
        <anio>1813</anio>
    </libro>
</biblioteca>

Resulting HTML (rendered)

✅ Transformation applied Order: ascending
Title Author Year
El Quijote Miguel de Cervantes 1605
Orgullo y prejuicio Jane Austen 1813
Cien anios de soledad Gabriel Garcia Marquez 1967

📖 Code Explanation

Complete PHP Code

<?php
$xmlDoc = new DOMDocument();
$xmlDoc->loadXML($xmlBiblioteca);

$xslDoc = new DOMDocument();
$xslDoc->loadXML($xslt);

$procesador = new XSLTProcessor();
$procesador->importStylesheet($xslDoc);
$procesador->setParameter('', 'orden', 'ascending');

echo $procesador->transformToXML($xmlDoc);
?>

📝 xsl:for-each and xsl:value-of

<xsl:for-each select="libro">
<xsl:value-of select="titulo"/>
</xsl:for-each>

What does it do? Iterates over each <libro> in the source XML and, for each one, extracts the value of titulo with xsl:value-of, generating an HTML table row.

📝 XSLT Parameters

<xsl:param name="orden" select="'ascending'"/>
$procesador->setParameter('', 'orden', 'descending');

What does it do? The <xsl:param> declares a variable that can be configured from outside the XSLT sheet. From PHP, setParameter() assigns it a value before transforming, letting you change the behavior (here, the order) without touching the XSLT.

💡 Concept: separating data, presentation and logic

The XML holds the data, the XSLT defines how to display it, and PHP simply orchestrates the transformation and passes parameters. This way you can change the presentation without touching the data.

🎯 Key Concepts Learned

XSLT

  • Transforms XML into HTML, text or other XML
  • Written in XML syntax
  • Uses templates (xsl:template)

xsl:sort and xsl:for-each

  • xsl:for-each iterates over nodes
  • xsl:sort sorts before iterating
  • data-type="number" sorts numerically

XSLTProcessor in PHP

  • importStylesheet() loads the XSLT
  • setParameter() passes dynamic values
  • transformToXML() runs the transformation

💪 Practical Exercise

Modify the transformation

  1. Switch between ascending and descending order and observe the resulting table
  2. Think about how you'd add one more column (for example, a row number) to the generated table
  3. How would you sort alphabetically by autor instead of by anio? (hint: change the select expression in xsl:sort and remove data-type="number")

Sort alphabetically by author

<xsl:sort select="autor" order="{$orden}"/>
<!-- Without data-type="number": it sorts as text, alphabetically -->