PHP XML Expat Parser
The built-in XML Expat Parser makes it possible to process XML documents in PHP.
The XML Expat Parser
The Expat parser is an event-based parser.Look at the following XML fraction:
<from>Jani</from> An event-based parser reports the XML above as a series of three events: - Start element: from
- Start CDATA section, value: Jani
- Close element: from
The XML File
The XML file "note.xml" will be used in the example below: <?xml version="1.0" encoding="UTF-8"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note> 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
// Initialize the XML parser$parser=xml_parser_create();
// Function to use at the start of an elementfunction start($parser,$element_name,$element_attrs) {
switch($element_name) {
case "NOTE":
echo "-- Note --<br>";
break;
case "TO":
echo "To: ";
break;
case "FROM":
echo "From: ";
break;
case "HEADING":
echo "Heading: ";
break;
case "BODY":
echo "Message: ";
}
}
// Function to use at the end of an elementfunction stop($parser,$element_name) {
echo "<br>";
}
// Function to use when finding character datafunction char($parser,$data) {
echo $data;
}
// Specify element handlerxml_set_element_handler($parser,"start","stop");
// Specify data handlerxml_set_character_data_handler($parser,"char");
// Open XML file$fp=fopen("note.xml","r");
// Read datawhile ($data=fread($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($parser)));
}
// Free the XML parserxml_parser_free($parser);
?> - Initialize the XML parser with the xml_parser_create() function
- Create functions to use with the different event handlers
- Add the xml_set_element_handler() function to specify which function will be executed when the parser encounters the opening and closing tags
- Add the xml_set_character_data_handler() function to specify which function will execute when the parser encounters character data
- Parse the file "note.xml" with the xml_parse() function
- In case of an error, add xml_error_string() function to convert an XML error to a textual description
- Call the xml_parser_free() function to release the memory allocated with the xml_parser_create() function
