Error handling with libxml error handling functions

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- Error handling with libxml error handling functions

## Error handling with libxml error handling functions

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);}?>

The above example will output something similar to:

    Libxml error: Invalid expression

    Libxml 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!'