xml_set_element_handler

(PHP 4, PHP 5, PHP 7, PHP 8)

xml_set_element_handler — Set up start and end element handlers

Description

xml_set_element_handler(XMLParser $parser, callable $start_handler, callable $end_handler): true

Sets the element handler functions for the XML parser.

start_handler is called when a new XML element is opened. end_handler is called when an XML element is closed.

Parameters

parser

The XML parser.

start_handler

If null or an empty string is passed, the handler is reset to its default state.

If handler is a callable, the callable is set as the handler.

If handler is a string, it can be the name of a method of an object set with xml_set_object().

The signature of the handler must be:

start_element_handler(XMLParser $parser, string $name, array $attributes): void

parser: The XML parser calling the handler.
name: Contains the name of the element for which this handler is called. If case-folding is in effect for this parser, the element name will be in uppercase letters.
attributes: An associative array with the element's attributes. The array is empty if the element has no attributes. The keys of this array are the attribute names, the values are the attribute values. Attribute names are case-folded on the same criteria as element names. Attribute values are not case-folded. The order in which attributes is traversed is identical to the order in which the attributes were declared.

end_handler

If null or an empty string is passed, the handler is reset to its default state.

If handler is a callable, the callable is set as the handler.

If handler is a string, it can be the name of a method of an object set with xml_set_object().

The signature of the handler must be:

end_element_handler(XMLParser $parser, string $name): void

parser: The XML parser calling the handler.
name: Contains the name of the element for which this handler is called. If case-folding is in effect for this parser, the element name will be in uppercase letters.

Return Values

Always returns true.

Changelog

Version	Description
8.0.0	`parser` expects an XMLParser instance now; previously, a valid `xml` resource was expected.

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User Contributed Notes 15 notes

down

rubentrancoso at gmail dot com ¶

17 years ago

My 25 cents. This example show how to parse a XML in a associative array tree.

<?php

$file = "flow/flow.xml";
$depth = 0;
$tree = array();
$tree['name'] = "root"; 
$stack[count($stack)] = &$tree;

function startElement($parser, $name, $attrs) {
   global $depth;
   global $stack;
   global $tree;

$element = array();
$element['name'] = $name;
   foreach ($attrs as $key => $value) { 
//echo $key."=".$value;
$element[$key]=$value;
    }

$last = &$stack[count($stack)-1];
$last[count($last)-1] = &$element;
$stack[count($stack)] = &$element;

$depth++;
}

function endElement($parser, $name) {
   global $depth;
   global $stack;

array_pop($stack);
$depth--;
}

$xml_parser = xml_parser_create();
xml_set_element_handler($xml_parser, "startElement", "endElement");
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);
$tree = $stack[0][0];
echo "<pre>";
print_r($tree);
echo "</pre>";

down

aw at avatartechnology dot com ¶

19 years ago

In response to landb at mail dot net...

As the notes mention, you can pass an array that contains the reference to an object and a method name when you need... so you can call methods in your own class as handlers like this:

xml_set_element_handler($parser, array($this,"_startElement"), array($this,"_endElement"));

Hope it helps...

down

youniforever at naver dot com ¶

19 years ago

<html> 
  <head> 
    <title>SAX Demonstration</title> 
   <META HTTP-EQUIV='Content-type' CONTENT='text/html; charset=euc-kr'> 
  </head> 
  <body> 
    <h1>RSS ??????</h1> 

<?php 

     $file = "data.xml"; 

$currentTag = ""; 
$currentAttribs = ""; 

      function startElement($parser, $name, $attribs) 
      { 
          global $currentTag, $currentAttribs; 
$currentTag = $name; 

$currentAttribs = $attribs; 
          switch ($name) { 

          default: 
              echo("<b>&lt$name&gt</b><br>"); 
              break; 
          } 
      } 

      function endElement($parser, $name) 
      { 
          global $currentTag; 
          switch ($name) { 
          default: 
              echo("<br><b>&lt/$name&gt</b><br><br>"); 
              break; 
          } 
$currentTag = ""; 
$currentAttribs = ""; 
      } 

      function characterData($parser, $data) 
      { 
          global $currentTag; 
          switch ($currentTag) { 
          case "link": 
              echo("<a href=\"$data\">$data</a>\n"); 
              break; 
          case "title": 
              echo("title : $data"); 
              break; 
          default: 
              echo($data); 
              break; 
          } 
      } 

$xmlParser = xml_parser_create(); 

$caseFold = xml_parser_get_option($xmlParser, 
XML_OPTION_CASE_FOLDING); 

$targetEncoding = xml_parser_get_option($xmlParser, 
XML_OPTION_TARGET_ENCODING); 

      if ($caseFold == 1) { 
xml_parser_set_option($xmlParser, XML_OPTION_CASE_FOLDING, false); 
      } 

xml_set_element_handler($xmlParser, "startElement", "endElement"); 
xml_set_character_data_handler($xmlParser, "characterData"); 

      if (!($fp = fopen($file, "r"))) { 
          die("Cannot open XML data file: $file"); 
      } 

     while ($data = fread($fp, 4096)) { 
          if (!xml_parse($xmlParser, $data, feof($fp))) { 
              die(sprintf("XML error: %s at line %d", 
xml_error_string(xml_get_error_code($xmlParser)), 
xml_get_current_line_number($xmlParser))); 
xml_parser_free($xmlParser); 
          } 
      } 
xml_parser_free($xmlParser); 
?> 
    </table> 
  </body> 
</html>

down

lloeki at gmail dot com ¶

17 years ago

I modified the previous script, so that it is associative. I find it more useful that way. BTW I prefer strtolower() things, but that's not mandatory at all.

<?php

$file = "data.xml";
$depth = 0;
$tree = array();
$tree['name'] = "root";
$stack[] = &$tree;

function startElement($parser, $name, $attrs) {
   global $depth;
   global $stack;
   global $tree;

$element = array();
   foreach ($attrs as $key => $value) {
$element[strtolower($key)]=$value;
   }

end($stack);
$stack[key($stack)][strtolower($name)] = &$element;
$stack[strtolower($name)] = &$element;

$depth++;
}

function endElement($parser, $name) {
   global $depth;
   global $stack;

array_pop($stack);
$depth--;
}

$xml_parser = xml_parser_create();
xml_set_element_handler($xml_parser, "startElement", "endElement");
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);
$tree = end(end($stack));
echo "<pre>";
print_r($tree);
echo "</pre>";

?>

down

hendra_g at hotmail dot com ¶

18 years ago

I ran into the same problem with 'ibjoel at hotmail dot com' in regards to self-closing tags, and found that the script that he/she wrote did not work as I expected.
I played around with some of php's functions and examples and compiled something, which may not be the neatest solution, but it works for the data that 'ibjoel at hotmail dot com' provided.
The data needs to be read from a file though, so the fp can be utilised. It still uses the xml_get_current_byte_index(resource parser) trick, but this time, I check for the last 2 character before the index and test if it's "/>".

<?php
/* myxmltest.xml:
<normal_tag>
  <self_close_tag />
     data
  <normal_tag>data
     <self_close_tag attr="value" />
  </normal_tag>
     data
  <normal_tag></normal_tag>
</normal_tag>
*/

//## Global Variables ##//
$file = "myxmltest.xml";
$character_data_on = false;
$tag_complete = true;

function startElement($parser, $name, $attrs) 
{
    global $character_data_on;
    global $tag_complete;

    echo "&lt;<font color=\"#0000cc\">$name</font>";
//## Print the attributes ##//
if (sizeof($attrs)) {
        while (list($k, $v) = each($attrs)) {
            echo " <font color=\"#009900\">$k</font>=\"<font 
                   color=\"#990000\">$v</font>\"";
        }
    }
//## Tag is still still incomplete,
    //## will be completed at either endElement or characterData ##//
$tag_complete = false;
$character_data_on = false;
}

function endElement($parser, $name) 
{
    global $fp;
    global $character_data_on;
    global $tag_complete;

//#### Test for self-closing tag ####//
    //## xml_get_current_byte_index(resource parser) when run in this
    //## function, gives the index at (indicated by *):
    //##   for self closing tag: <br />*
    //##   for individual closing tag: <div>character data*</div>
    //## So to test for self-closing tag, we can just test for the last 2 
    //## characters from the index
    //###################################//

if (!$character_data_on) {
//## Record current fp position ##//
$temp_fp = ftell($fp);

//## Point fp to 2 bytes before the end element byte index ##//
$end_element_byte_index = xml_get_current_byte_index($parser);
fseek($fp,$end_element_byte_index-2);

//## Gets the last 2 characters before the end element byte index ##//
$validator = fgets($fp, 3);

//## Restore fp position ##//
fseek($fp,$temp_fp);

//## If the last 2 character is "/>" ##//
if ($validator=="/>") {
//// Complete the self-closing tag ////
echo " /&gt";
//// Otherwise it is an individual closing tag ////
} else echo "&gt&lt/<font color=\"#0000cc\">$name</font>&gt";
$tag_complete = true;
    } else echo "&lt/<font color=\"#0000cc\">$name</font>&gt";

$character_data_on = false;
}

function characterData($parser, $data) 
{
    global $character_data_on;
    global $tag_complete;

    if ((!$character_data_on)&&(!$tag_complete)) {
        echo "&gt";
$tag_complete = true;
    }
    echo "<b>$data</b>"; 
$character_data_on = true;
}

$xml_parser = xml_parser_create();
xml_parser_set_option($xml_parser, XML_OPTION_CASE_FOLDING, false);
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");
}

echo "<pre>";
while ($file_content = fread($fp, 4096)) {
    if (!xml_parse($xml_parser, $file_content, feof($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)));
    }
}
echo "</pre>";
xml_parser_free($xml_parser);
?>

down

jg at jmkg dot net ¶

23 years ago

If you are using a class for xml parsing, and want to check the return value of xml_set_element_handler in case it  fails, you must do this outside of the class's constructor. Inside the constructor, PHP-4.0.5 will die.


Basically, put all your xml initialisation code in another function of the class, and keep it out of the constructor.

down

darien at etelos dot com ¶

17 years ago

This documentation is somewhat awry. I know it's been said many times before, but it bears repeating...

If using PHP4, you may be required to use xml_set_object() instead of calling any of the xml_set_*_handler() functions with a two-item array. It will work fine on PHP5, but move the same code to PHP4 and it will create one copie of $this (even if you use &$this) for each handler you set!

<?php
// This code will fail mysteriously on PHP4.
$this->parser = xml_parser_create();
xml_set_element_handler(
$this->parser,
            array(&$this,"start_tag"),
            array(&$this,"end_tag")
        );
xml_set_character_data_handler(
$this->parser,
            array(&$this,"tag_data")
        );
?>

<?php
// This code will work on PHP4.
$this->parser = xml_parser_create();
xml_set_object($this->parser,&$this); 
xml_set_element_handler(
$this->parser,
"start_tag",
"end_tag"
);
xml_set_character_data_handler(
$this->parser,
"tag_data"
);
?>

down

turan dot yuksel at tcmb dot gov dot tr ¶

18 years ago

The method that 'ibjoel at hotmail dot com' have described requires libxml2 as the xml parser, it does not work with expat. For a brief explanation, see xml_get_current_byte_index.

down

ibjoel at hotmail dot com ¶

19 years ago

I noticed that in the example below, and all the examples I've seen on this site for viewing xml in html, the look of self closing tags such as <br /> are not preserved. The parser cannot distinguish between <tag /> and <tag></tag>, and if your start and end element functions are like these examples, both instances will be output with both an indvidual start and end tag.  I needed to preserve self-closing tags and it took me a while to figure out this work around. Hope this helps someone...

The start tag is left open, and then completed by it's first child, the next start tag or its end tag.  The end tag will complete with " />", or </tag> depending on the number of bytes between the start and end tags in the parsed data.
<?php
//$data=filepath or string
$data=<<<DATA
<normal_tag>
  <self_close_tag />
      data
  <normal_tag>data
     <self_close_tag attr="value" />
  </normal_tag>
      data
  <normal_tag></normal_tag>
</normal_tag>
DATA;

function startElement($parser, $name, $attrs)
{
xml_set_character_data_handler($parser, "characterData");
        global $first_child, $start_byte;
        if($first_child)          //close start tag if neccessary
echo "><br />";
$first_child=true;
$start_byte=xml_get_current_byte_index ($parser);
        if(count($attrs)>=1){
                foreach($attrs as $x=>$y){
$attr_string .= " $x=\"$y\"";
                }
        }
        echo htmlentities("<{$name}{$attr_string}"); //unclosed starttag
}

function endElement($parser, $name)
{
        global $first_child, $start_byte;
$byte=xml_get_current_byte_index ($parser);
        if($byte-$start_byte>2){           //if end tag is more than 2 bytes from start tag
if($first_child)          //close start tag if neccessary
echo "><br />";
                echo htmlentities("</{$name}>")."<br />";  //individual end tag
}else
                echo " /><br />";  // self closing tag
$first_child=false;

}

function characterData($parser, $data)
{
        global $first_child;
        if($first_child)  //if $data is first child, close start tag
echo "><br />";
        if($data=trim($data))
                echo "<font color='blue'>$data</font><br />";
$first_child=false;
}

function ParseData($data)
{
$xml_parser = xml_parser_create();
xml_set_element_handler($xml_parser, "startElement", "endElement");
xml_parser_set_option($xml_parser,XML_OPTION_CASE_FOLDING,0);
        if(is_file($data))
        {
                if (!($fp = fopen($file, "r"))) {
                        die("could not open XML input");
                }

                while ($data = fread($fp, 4096)) {
                        if (!xml_parse($xml_parser, $data, feof($fp))) {
$error=xml_error_string(xml_get_error_code($xml_parser));
$line=xml_get_current_line_number($xml_parser);
                                die(sprintf("XML error: %s at line %d",$error,$line));
                        }
                }
        }else{
                if (!xml_parse($xml_parser, $data, 1)) {
$error=xml_error_string(xml_get_error_code($xml_parser));
$line=xml_get_current_line_number($xml_parser);
                                die(sprintf("XML error: %s at line %d",$error,$line));
                }
        }

xml_parser_free($xml_parser);
}

ParseData($data);
?>

down

tj at tobyjoe dot com ¶

21 years ago

It seems that the tag handlers don't block on one another (the end handler is called whether or not the begin handler has finished). this can put you in a tight spot if you don't realize it while planning your app.

down

-1

kok at nachon dot nl ¶

15 years ago

Here is another example of detecting empty elements. I works with libxml2. Note that it handles buffer boundaries.

<?php

$depth = 0; //current depth, used for pretty printing
$empty = false; //whether the tag is empty
$offset = 0; //the index of the start of the current buffer within the stream

function tagStart($parser, $name, array $attribs) {
    global $depth, $empty, $data, $offset, $lastchar;
$idx = xml_get_current_byte_index($parser);
/* xml_get_current_byte_index returns index within the streams and not
       within the buffer.*/

    /* Check if the index is within the buffer. */
if (isset($data[$idx - $offset])) {
$c = $data[$idx - $offset];
    } else {
/* If it isn't simple use the last character of the buffer. */
$c = $lastchar;
    }
$empty = $c == '/';
    echo str_repeat("\t", $depth), "<$name", ($empty ? '/>' : '>'), "\n";
    if (!$empty) ++$depth;
}

function tagEnd($parser, $name) {
    global $depth, $empty;
    if (!$empty) {
        --$depth;
        echo str_repeat("\t", $depth), "</$name>\n";
    } else {
$empty = false;
    }
}

$parser = xml_parser_create();
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, false);
xml_set_element_handler($parser, 'tagStart', 'tagEnd');

$data1 = '
<test>
    <empty att="3" />
    <nocontent></nocontent>
    <content>
        <empty/>
        <empty/>
    </content>
    <empty/';

$data2 = '>
    <empty att="5" />
</test>
';

$data = &$data1;
$length = strlen($data1);
$lastchar = $data[$length-1];
xml_parse($parser, $data1);
$offset .= $length;
$data = &$data2;
xml_parse($parser, $data2);

down

-2

vladimir-leontiev at uiowa dot edu ¶

18 years ago

It seems that characterData() gets characters in chuncks of 1024; therefore if you have string of characters between you tags that is longer than 1024 then characterData() will be called more that once for single pair of tags. I don't know if this feature(bug?) is documented anywhere, I just wanted to warn everyone about this; it had tripped me. I use php 4.3.10 on Linux.

down

-1

redb ¶

18 years ago

Example below (BadParser) works fine with some changes.

xml_set_element_handler ( $parser, array ( &$this, 'tagStart' ), array ( &$this, 'tagEnd' ) );
xml_set_character_data_handler ( $parser, array ( &$this, 'tagContent' ) );

down

-2

Anonymous ¶

19 years ago

In response to aw at avatartechnology dot com...
In response to landb at mail dot net...

When your functions are in an object:
Careful ! Don't forget to add: & (reference) to your parameters.

xml_set_element_handler($parser, array(&$this,"_startElement"), array(&$this,"_endElement"));
--> xmlparse will work on your object (good).

instead of:
xml_set_element_handler($parser, array($this,"_startElement"), array($this,"_endElement"));
---> xmlparse will work on a COPY of your object (often bad)

Vin-s
(sorry for my english)

down

-2

Anonymous ¶

22 years ago

You CAN use classes to parse XML. Just take a look at the following function:


xml_set_object

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