9.4 PHP XML Expat

Initializing the XML Expat Parser

We want to initialize the XML Expat Parser in PHP, define some handlers for different XML events, and then parse the XML file.

Example: PHP XML Expat - The XML Expat Parser

<?php
// Initialize the XML parser
$parser=xml_parser_create();

// Function to use at the start of an element
function start($parser,$element_name,$element_attrs) {
  switch($element_name) {
    case "NOTE":
    echo "-- Note --<br>";
    break;
    case "TO":
    echo "To: ";
    break;
    case "FROM":
    echo "From: ";
    break;
    case "HEADING":
    echo "Heading: ";
    break;
    case "BODY":
    echo "Message: ";
  }
}

// Function to use at the end of an element
function stop($parser,$element_name) {
  echo "<br>";
}

// Function to use when finding character data
function char($parser,$data) {
  echo $data;
}

// Specify element handler
xml_set_element_handler($parser,"start","stop");

// Specify data handler
xml_set_character_data_handler($parser,"char");

// Open XML file
$fp=fopen("note.xml","r");

// Read data
while ($data=fread($fp,4096)) {
  xml_parse($parser,$data,feof($fp)) or
  die (sprintf("XML Error: %s at line %d",
  xml_error_string(xml_get_error_code($parser)),
  xml_get_current_line_number($parser)));
}

// Free the XML parser
xml_parser_free($parser);
?>

• Example explained:
  1. Initialize the XML parser with the xml_parser_create() function
  2. Create functions to use with the different event handlers
  3. Add the xml_set_element_handler() function to specify which function will be executed when the parser encounters the opening and closing tags
  4. Add the xml_set_character_data_handler() function to specify which function will execute when the parser encounters character data
  5. Parse the file "note.xml" with the xml_parse() function
  6. In case of an error, add xml_error_string() function to convert an XML error to a textual description
  7. Call the xml_parser_free() function to release the memory allocated with the xml_parser_create() function

More PHP XML Expat Parser

For more information about the PHP Expat functions, visit W3Schools.com PHP XML Parser Reference.