XMLReader::setRelaxNGSchemaSource

If you get the following warning message when calling ->setRelaxNGSchemaSource(): "Warning: XMLReader::setRelaxNGSchemaSource()
[xmlreader.setrelaxngschemasource]: Unable to set schema. This must be
set prior to reading or schema contains errors." 

Make sure to load data using XMLReader::open() or XMLReader::xml() prior to calling XMLReader::setRelaxNGSchemaSource().

Cf. comment on XMLReader::setRelaxNGSchema for more details.

This function and setRelaxNGSchema() seem picky about when they are called - right after the call to open(). For example:

<?php
  $schema="/path/to/schema.rng";
  $xmlfile="/path/to/xml.xml";

  $xml = new XMLReader();
  $xml->open($xmlfile);
  $xml->setRelaxNGSchemaSource(file_get_contents($schema));
 
  while ($xml->read()) {
   // ...
  }
 
  $xml->close();
?>