How to read XML Document using the XML Parser extension in PHP

Background

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With XML Parser, you use callback functions to deal with specific events such as when the start or end of an XML element is encountered. These functions are registered using API functions made available for the XML Parser extension and are triggered or executed when a specific event is encountered. Also, you can only read XML with this extension.

Software Requirements

Windows 7 Professional SP1
PHP 5.5.9 / Zend Engine v2.5.0
NetBeans IDE 8.0.1
ApacheFriends XAMPP Version 1.8.3
- Apache/2.4.7 (Win32) / Open SSL/1.0.1e

XML Parser

The basic steps in reading an XML document using XML Parser are as follow:

Create a new parser resource by calling the xml_parser_create() function
PHP
// Creates a parser resource $parser = xml_parser_create();
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// Creates a parser resource
$parser = xml_parser_create();

Create two callback functions to handle the start and end of an XML document, and register them with the parser using the xml_set_element_handler() function.

function startElement($parser, $element, $attributes) {
    echo "Start of Element: $element\n";
    foreach($attributes as $key=>$value) {
        echo "    Attribute: $key | value: $value \n";
    }
}

function endElement($parser, $element) {
    echo "End of Element: $element\n";
}

xml_set_element_handler($parser, "startElement", "endElement");

function startElement($parser, $element, $attributes) {

echo "Start of Element: $element\n";

foreach($attributes as $key=>$value) {

echo " Attribute: $key | value: $value \n";

}

function endElement($parser, $element) {

echo "End of Element: $element\n";

}

xml_set_element_handler($parser, "startElement", "endElement");

Create another callback function to handle any character data within an element, and register it with the parser using xml_set_character_data_handler() function.
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PHP
function characterDataHandler($parser, $data ) { echo "Data: $data \n"; } xml_set_character_data_handler( $parser, "characterDataHandler");
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function characterDataHandler($parser, $data ) {
echo "Data: $data \n";
}
xml_set_character_data_handler( $parser, "characterDataHandler");
Parse the XML document using xml_parse() function and passing the parser resource and the XML string to parse.
PHP
xml_parse($parser, "<note><to>Tove</to><from>Jani</from><heading>Reminder</heading><body>Don't forget me this weekend!</body></note>");
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xml_parse($parser, "<note><to>Tove</to><from>Jani</from><heading>Reminder</heading><body>Don't forget me this weekend!</body></note>");
Destroy the parser
PHP
xml_parser_free($parser);
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xml_parser_free($parser);

When executed as PHP file, the codes above output the following:

Start of Element: NOTE
Start of Element: TO
Data: Tove 
End of Element: TO
Start of Element: FROM
Data: Jani 
End of Element: FROM
Start of Element: HEADING
Data: Reminder 
End of Element: HEADING
Start of Element: BODY
Data: Don't forget me this weekend! 
End of Element: BODY
End of Element: NOTE

Start of Element: NOTE

Start of Element: TO

Data: Tove

End of Element: TO

Start of Element: FROM

Data: Jani

End of Element: FROM

Start of Element: HEADING

Data: Reminder

End of Element: HEADING

Start of Element: BODY

Data: Don't forget me this weekend!

End of Element: BODY

End of Element: NOTE

Dealing with Parse Errors

The xml_parse() function returns either true or false. If it returns false, there was a problem encountered while parsing the XML. The details of the problem can be determine using some other XML Parser functions:

xml_get_error_code($parser)
This returns an error code of the last error encountered
xml_error_string($code)
This returns the string describing the error code returned by xml_get_error_code()
xml_get_current_line_number($parser) and xml_get_current_column_number($parser)
These returns the location of the cause of the error in the XML
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Background

Software Requirements

XML Parser

Dealing with Parse Errors

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