PHP | XMLReader setSchema() Function

The XMLReader::setSchema() function is an inbuilt function in PHP which is used to validate the document using a XSD schema. This XSD schema is nothing but a file that defines the rule for the XML structure and should be in the form of .xsd file.

Syntax:

bool XMLReader::setSchema( string $filename )

Parameters: This function accepts a single parameter $filename which holds the XSD filename.

Return Value: This function returns TRUE on success or FALSE on failure.

Exceptions: This function throws E_WARNING if libxml extension was compiled without schema support.

Below examples illustrate the XMLReader::setSchema() function in PHP:

Example 1:

• data.xml ( The XML file to be validated )

  <?xml version="1.0"?>
  <student>
      <name>Rahul</name>
      <rollno>1726262</rollno>
  </student>
• rule.xsd ( The rules to be followed by the XML file )

  <?xml version="1.0"?>
  <xs:schema xmlns:xs=
        "http://www.w3.org/2001/XMLSchema"
  elementFormDefault="qualified">
      <xs:element name="student">
          <xs:complexType>
              <xs:sequence>
                  <xs:element name="name"
                      type="xs:string"/>
                  <xs:element name="rollno"
                     type="xs:integer"/>
              </xs:sequence>
          </xs:complexType>
      </xs:element>
  </xs:schema>
• index.php ( The PHP script to run the validation )

  <?php
  
  // Create a new XMLReader instance
  $XMLReader = new XMLReader();
  
  // Open the XML file
  $XMLReader->open('data.xml');
  
  // Load the rule
  $XMLReader->setSchema('rule.xsd');
  
  // Iterate through the XML nodes
  while ($XMLReader->read()) {
      if ($XMLReader->nodeType == XMLREADER::ELEMENT) {
  
          // Check if XML follows the XSD rule
          if ($XMLReader->isValid()) {
              echo "This document is valid!<br>";
          }
  
      }
  }
  ?>
• Output:

  This document is valid!
  This document is valid!
  This document is valid!

Example 2:

• data.xml

  <?xml version="1.0"?>
  <div>
      <phoneNo>This should not be text</phoneNo>
  </div>
• rule.xsd

  <?xml version="1.0"?>
  <xs:schema xmlns:xs=
        "http://www.w3.org/2001/XMLSchema"
  elementFormDefault="qualified">
      <xs:element name="div">
          <xs:complexType>
              <xs:sequence>
                  <xs:element name="phoneNo"
                     type="xs:integer"/>
              </xs:sequence>
          </xs:complexType>
      </xs:element>
  </xs:schema>
• index.php

  <?php
  
  // Create a new XMLReader instance
  $XMLReader = new XMLReader();
  
  // Open the XML file
  $XMLReader->open('data.xml');
  
  // Load the rule
  $XMLReader->setSchema('rule.xsd');
  
  // Iterate through the XML nodes
  while ($XMLReader->read()) {
      if ($XMLReader->nodeType == XMLREADER::ELEMENT) {
  
          // Check if XML follows the XSD rule
          if (!$XMLReader->isValid()) {
              echo "This document is not valid!<br>";
          }
  
      }
  }
  ?>
• Output:

  This document is not valid!
  This document is not valid!

Reference: https://www.php.net/manual/en/xmlreader.setschema.php