PHP - libxml_set_external_entity_loader() Function

Definition and Usage

XML is a mark-up language to share the data across the web, XML is for both human read-able and machine read-able. The libXMLError class contains the errors thrown by the libxml library.

The libxml_set_external_entity_loader() function is used to change the default external entity loader.

Syntax

libxml_set_external_entity_loader($function);

Parameters

Sr.No	Parameter & Description
1	function(Mandatory) This is a callable function with 3 arguments namely, public id, system id, and a context.

Return Values

This function returns a boolean value which is TRUE incase of success and FALSE incase of a failure.

PHP Version

This function was first introduced in PHP Version 5 and works in all the later versions.

Example

Following example demonstrates the usage of the libxml_set_external_entity_loader() function −

<html>
   <head>
      <body>
         <?php
            $str = <<<XML
            <!DOCTYPE test PUBLIC "-//TEST/BAR" "http://test.com/testbar">
            <test>bar</test>
            $dtd = <<<DTD
            <!ELEMENT test (#PCDATA)>
            libxml_set_external_entity_loader(
            function ($public, $sys, $context) use($dtd) {
               print_r($public);
               print_r($sys);
               print_r($context);
               $f = fopen("php://temp", "r+");
               fwrite($f, $dtd);
               rewind($f);
               return $f;
            } 
         );
         $doc = new DOMDocument;
         $r =  $doc->loadXML($str);
         print_r($doc->validate());
         ?>      
      </body>
   </head>   
</html>

This will produce following result −

-//TEST/BARhttp://test.com/testbarArray ( 
   [directory] => [intSubName] => [extSubURI] => [extSubSystem] => ) 1

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