XML parser functions XML
&reftitle.intro; XML (eXtensible Markup Language) is a data format for structured document interchange on the Web. It is a standard defined by The World Wide Web consortium (W3C). Information about XML and related technologies can be found at &url.xml;. This PHP extension implements support for James Clark's expat in PHP. This toolkit lets you parse, but not validate, XML documents. It supports three source character encodings also provided by PHP: US-ASCII, ISO-8859-1 and UTF-8. UTF-16 is not supported. This extension lets you create XML parsers and then define handlers for different XML events. Each XML parser also has a few parameters you can adjust.
&reftitle.required; This extension uses expat, which can be found at &url.expat;. The Makefile that comes with expat does not build a library by default, you can use this make rule for that: A source RPM package of expat can be found at &url.expat.rpm;.
&reftitle.install; If you are using Apache-1.3.7 or later, you already have the required expat library. Simply configure PHP using (without any additional path) and it will automatically use the expat library built into Apache. On UNIX, run configure with the option. The expat library should be installed somewhere your compiler can find it. If you compile PHP as a module for Apache 1.3.9 or later, PHP will automatically use the bundled expat library from Apache. You may need to set CPPFLAGS and LDFLAGS in your environment before running configure if you have installed expat somewhere exotic. Build PHP. Tada! That should be it.
&reftitle.runtime; &no.config;
&reftitle.resources; &no.resource;
&reference.xml.constants;
Event Handlers The XML event handlers defined are: Supported XML handlers PHP function to set handler Event description xml_set_element_handler Element events are issued whenever the XML parser encounters start or end tags. There are separate handlers for start tags and end tags. xml_set_character_data_handler Character data is roughly all the non-markup contents of XML documents, including whitespace between tags. Note that the XML parser does not add or remove any whitespace, it is up to the application (you) to decide whether whitespace is significant. xml_set_processing_instruction_handler PHP programmers should be familiar with processing instructions (PIs) already. <?php ?> is a processing instruction, where php is called the "PI target". The handling of these are application-specific, except that all PI targets starting with "XML" are reserved. xml_set_default_handler What goes not to another handler goes to the default handler. You will get things like the XML and document type declarations in the default handler. xml_set_unparsed_entity_decl_handler This handler will be called for declaration of an unparsed (NDATA) entity. xml_set_notation_decl_handler This handler is called for declaration of a notation. xml_set_external_entity_ref_handler This handler is called when the XML parser finds a reference to an external parsed general entity. This can be a reference to a file or URL, for example. See the external entity example for a demonstration.
Case Folding The element handler functions may get their element names case-folded. Case-folding is defined by the XML standard as "a process applied to a sequence of characters, in which those identified as non-uppercase are replaced by their uppercase equivalents". In other words, when it comes to XML, case-folding simply means uppercasing. By default, all the element names that are passed to the handler functions are case-folded. This behaviour can be queried and controlled per XML parser with the xml_parser_get_option and xml_parser_set_option functions, respectively.
Error Codes The following constants are defined for XML error codes (as returned by xml_parse): XML_ERROR_NONE XML_ERROR_NO_MEMORY XML_ERROR_SYNTAX XML_ERROR_NO_ELEMENTS XML_ERROR_INVALID_TOKEN XML_ERROR_UNCLOSED_TOKEN XML_ERROR_PARTIAL_CHAR XML_ERROR_TAG_MISMATCH XML_ERROR_DUPLICATE_ATTRIBUTE XML_ERROR_JUNK_AFTER_DOC_ELEMENT XML_ERROR_PARAM_ENTITY_REF XML_ERROR_UNDEFINED_ENTITY XML_ERROR_RECURSIVE_ENTITY_REF XML_ERROR_ASYNC_ENTITY XML_ERROR_BAD_CHAR_REF XML_ERROR_BINARY_ENTITY_REF XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF XML_ERROR_MISPLACED_XML_PI XML_ERROR_UNKNOWN_ENCODING XML_ERROR_INCORRECT_ENCODING XML_ERROR_UNCLOSED_CDATA_SECTION XML_ERROR_EXTERNAL_ENTITY_HANDLING
Character Encoding PHP's XML extension supports the Unicode character set through different character encodings. There are two types of character encodings, source encoding and target encoding. PHP's internal representation of the document is always encoded with UTF-8. Source encoding is done when an XML document is parsed. Upon creating an XML parser, a source encoding can be specified (this encoding can not be changed later in the XML parser's lifetime). The supported source encodings are ISO-8859-1, US-ASCII and UTF-8. The former two are single-byte encodings, which means that each character is represented by a single byte. UTF-8 can encode characters composed by a variable number of bits (up to 21) in one to four bytes. The default source encoding used by PHP is ISO-8859-1. Target encoding is done when PHP passes data to XML handler functions. When an XML parser is created, the target encoding is set to the same as the source encoding, but this may be changed at any point. The target encoding will affect character data as well as tag names and processing instruction targets. If the XML parser encounters characters outside the range that its source encoding is capable of representing, it will return an error. If PHP encounters characters in the parsed XML document that can not be represented in the chosen target encoding, the problem characters will be "demoted". Currently, this means that such characters are replaced by a question mark.
&reftitle.examples; Here are some example PHP scripts parsing XML documents.
XML Element Structure Example This first example displays the stucture of the start elements in a document with indentation. Show XML Element Structure
XML Tag Mapping Example Map XML to HTML This example maps tags in an XML document directly to HTML tags. Elements not found in the "map array" are ignored. Of course, this example will only work with a specific XML document type. "B", "EMPHASIS" => "I", "LITERAL" => "TT" ); function startElement($parser, $name, $attrs) { global $map_array; if ($htmltag = $map_array[$name]) { print "<$htmltag>"; } } function endElement($parser, $name) { global $map_array; if ($htmltag = $map_array[$name]) { print ""; } } function characterData($parser, $data) { print $data; } $xml_parser = xml_parser_create(); // use case-folding so we are sure to find the tag in $map_array xml_parser_set_option($xml_parser, XML_OPTION_CASE_FOLDING, true); xml_set_element_handler($xml_parser, "startElement", "endElement"); xml_set_character_data_handler($xml_parser, "characterData"); if (!($fp = fopen($file, "r"))) { die("could not open XML input"); } while ($data = fread($fp, 4096)) { if (!xml_parse($xml_parser, $data, feof($fp))) { die(sprintf("XML error: %s at line %d", xml_error_string(xml_get_error_code($xml_parser)), xml_get_current_line_number($xml_parser))); } } xml_parser_free($xml_parser); ]]>
XML External Entity Example This example highlights XML code. It illustrates how to use an external entity reference handler to include and parse other documents, as well as how PIs can be processed, and a way of determining "trust" for PIs containing code. XML documents that can be used for this example are found below the example (xmltest.xml and xmltest2.xml.) External Entity Example $name"; if (sizeof($attribs)) { while (list($k, $v) = each($attribs)) { print " $k=\"$v\""; } } print ">"; } function endElement($parser, $name) { print "</$name>"; } function characterData($parser, $data) { print "$data"; } function PIHandler($parser, $target, $data) { switch (strtolower($target)) { case "php": global $parser_file; // If the parsed document is "trusted", we say it is safe // to execute PHP code inside it. If not, display the code // instead. if (trustedFile($parser_file[$parser])) { eval($data); } else { printf("Untrusted PHP code: %s", htmlspecialchars($data)); } break; } } function defaultHandler($parser, $data) { if (substr($data, 0, 1) == "&" && substr($data, -1, 1) == ";") { printf('%s', htmlspecialchars($data)); } else { printf('%s', htmlspecialchars($data)); } } function externalEntityRefHandler($parser, $openEntityNames, $base, $systemId, $publicId) { if ($systemId) { if (!list($parser, $fp) = new_xml_parser($systemId)) { printf("Could not open entity %s at %s\n", $openEntityNames, $systemId); return false; } while ($data = fread($fp, 4096)) { if (!xml_parse($parser, $data, feof($fp))) { printf("XML error: %s at line %d while parsing entity %s\n", xml_error_string(xml_get_error_code($parser)), xml_get_current_line_number($parser), $openEntityNames); xml_parser_free($parser); return false; } } xml_parser_free($parser); return true; } return false; } function new_xml_parser($file) { global $parser_file; $xml_parser = xml_parser_create(); xml_parser_set_option($xml_parser, XML_OPTION_CASE_FOLDING, 1); xml_set_element_handler($xml_parser, "startElement", "endElement"); xml_set_character_data_handler($xml_parser, "characterData"); xml_set_processing_instruction_handler($xml_parser, "PIHandler"); xml_set_default_handler($xml_parser, "defaultHandler"); xml_set_external_entity_ref_handler($xml_parser, "externalEntityRefHandler"); if (!($fp = @fopen($file, "r"))) { return false; } if (!is_array($parser_file)) { settype($parser_file, "array"); } $parser_file[$xml_parser] = $file; return array($xml_parser, $fp); } if (!(list($xml_parser, $fp) = new_xml_parser($file))) { die("could not open XML input"); } print "
";
while ($data = fread($fp, 4096)) {
    if (!xml_parse($xml_parser, $data, feof($fp))) {
        die(sprintf("XML error: %s at line %d\n",
                    xml_error_string(xml_get_error_code($xml_parser)),
                    xml_get_current_line_number($xml_parser)));
    }
}
print "
"; print "parse complete\n"; xml_parser_free($xml_parser); ?> ]]>
xmltest.xml ]> Title &plainEntity; a1b1c1 a2c2 a3b3c3 &systemEntity;
About this Document
]]>
This file is included from xmltest.xml: xmltest2.xml ]> &testEnt; ]]>
&reference.xml.functions;