xml_set_character_data_handler()
The xml_set_character_data_handler() function is a PHP built-in function that sets a user-defined function as the handler for character data in an XML parser. It belongs to the legacy xml extension (based on the Expat parser) and is used to set a custom function to handle character data during stream-based XML parsing.
This function is useful when you need to manipulate character data during parsing, for example, to trim whitespace or perform other transformations on the extracted text.
Syntax
xml_set_character_data_handler($parser, $handler)Where $parser is the XML parser resource, and $handler is the name of the user-defined function that will handle the character data. Note that the handler function will receive three arguments: $parser, $data, and $length.
Usage Examples
Let's take a look at a practical example of using xml_set_character_data_handler() in PHP.
Example: Setting a Character Data Handler Function
Suppose you want to parse an XML string using the legacy xml extension. You can use xml_parser_create() to create a new parser, set a character data handler using xml_set_character_data_handler(), and then parse the data:
Setting a Character Data Handler Function in PHP
function handle_character_data($parser, $data, $length) {
// Trim whitespace and output the character data
echo trim($data);
}
$xml_parser = xml_parser_create();
xml_set_character_data_handler($xml_parser, "handle_character_data");
$xml_data = '<root><item>Hello World</item></root>';
xml_parse($xml_parser, $xml_data, true);
xml_parser_free($xml_parser);This code creates a new XML parser using xml_parser_create(). It then sets a custom function handle_character_data() to handle the character data in the XML. The function receives the parser resource, the character data string, and the length of the data chunk. Finally, xml_parse() processes the XML, and xml_parser_free() cleans up the parser resource.
Conclusion
In this article, we've discussed PHP's xml_set_character_data_handler() function and how it sets a callback for character data in the legacy Expat-based xml extension. We've covered its syntax and provided a complete parsing example. Note that this is a legacy API; for new projects, consider using modern alternatives like DOMDocument or SimpleXML. When working with the xml extension, this function allows you to manipulate character data, trim whitespace, or apply transformations during stream-based parsing.
Practice
What does the 'xml_set_character_data_handler()' function do in PHP?