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
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:
<?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
$parser=xml_parser_create();
//
Function to use at the start of an element
function
start($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:
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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