Error handling with libxml error handling functions

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libxml offers a number of functions for handling errors, which can be employed to capture and deal with errors in XSLT processing.

Example #1 fruits.xml

A valid XML file.

<fruits>
 <fruit>Apple</fruit>
 <fruit>Banana</fruit>
 <fruit>Cherry</fruit>
</fruits>

Example #2 fruits.xsl

Contains an invalid select expression.

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="html" encoding="utf-8" indent="no"/>
 <xsl:template match="fruits">
  <ul>
   <xsl:apply-templates/>
  </ul>
 </xsl:template>
 <xsl:template match="fruit">
  <li><xsl:value-of select="THIS IS A DELIBERATE ERROR!"/></li>
 </xsl:template>
</xsl:stylesheet>

Example #3 Collating and printing errors

The example below captures and displays libxml errors raised when calling XSLTProcessor::importStyleSheet() with a stylesheet containing an error.

  <?php

$xmldoc  = new  DOMDocument ();
 $xsldoc  = new  DOMDocument ();
 $xsl  = new  XSLTProcessor ();

 $xmldoc -> loadXML ( 'fruits.xml' );
 $xsldoc -> loadXML ( 'fruits.xsl' );

 libxml_use_internal_errors ( true );
 $result  =  $xsl -> importStyleSheet ( $xsldoc );
if (! $result ) {
    foreach ( libxml_get_errors () as  $error ) {
        echo  "Libxml error:  { $error -> message } \n" ;
    }
}
 libxml_use_internal_errors ( false );

if ( $result ) {
    echo  $xsl -> transformToXML ( $xmldoc );
}

 ?>

以上例程的输出类似于：

Libxml error: Invalid expressionLibxml error: compilation error: file fruits.xsl line 9 element value-of
Libxml error: xsl:value-of : could not compile select expression 'THIS IS A DELIBERATE ERROR!'