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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:
Jani
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 Expat Parser functions are part of the PHP core. There is no installation needed to use these functions.
The XML File
The XML file “note.xml” will be used in the example below:
Tove
Jani
Reminder
Don’t forget me this weekend!
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
$parser=xml_parser_create();
// Function to use at the start of an element
function start($parser,$element_name,$element_attrs) {
switch($element_name) {
case “NOTE”:
echo “– Note —
“;
break;
case “TO”:
echo “To: “;
break;
case “FROM”:
echo “From: “;
break;
case “HEADING”:
echo “Heading: “;
break;
case “BODY”:
echo “Message: “;
}
}
// Function to use at the end of an element
function stop($parser,$element_name) {
echo “
“;
}
// Function to use when finding character data
function char($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:
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
More PHP XML Expat Parser
For more information about the PHP Expat functions, visit our PHP XML Parser Reference.
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