Title: AtomParser
Published: April 25, 2014
Last modified: February 24, 2026

---

# class AtomParser {}

## In this article

 * [Methods](https://developer.wordpress.org/reference/classes/AtomParser/?output_format=md#methods)
 * [Source](https://developer.wordpress.org/reference/classes/AtomParser/?output_format=md#source)

[ Back to top](https://developer.wordpress.org/reference/classes/AtomParser/?output_format=md#wp--skip-link--target)

AtomLib Atom Parser API

## 󠀁[Methods](https://developer.wordpress.org/reference/classes/AtomParser/?output_format=md#methods)󠁿

| Name | Description | 
| [AtomParser::__construct](https://developer.wordpress.org/reference/classes/atomparser/__construct/) | PHP5 constructor. | 
| [AtomParser::_default](https://developer.wordpress.org/reference/classes/atomparser/_default/) | – | 
| [AtomParser::_p](https://developer.wordpress.org/reference/classes/atomparser/_p/) | – | 
| [AtomParser::AtomParser](https://developer.wordpress.org/reference/classes/atomparser/atomparser/) | PHP4 constructor. | 
| [AtomParser::cdata](https://developer.wordpress.org/reference/classes/atomparser/cdata/) | – | 
| [AtomParser::end_element](https://developer.wordpress.org/reference/classes/atomparser/end_element/) | – | 
| [AtomParser::end_ns](https://developer.wordpress.org/reference/classes/atomparser/end_ns/) | – | 
| [AtomParser::error_handler](https://developer.wordpress.org/reference/classes/atomparser/error_handler/) | – | 
| [AtomParser::is_declared_content_ns](https://developer.wordpress.org/reference/classes/atomparser/is_declared_content_ns/) | – | 
| [AtomParser::map_attrs](https://developer.wordpress.org/reference/classes/atomparser/map_attrs/) | Map attributes to key=”val” | 
| [AtomParser::map_xmlns](https://developer.wordpress.org/reference/classes/atomparser/map_xmlns/) | Map XML namespace to string. | 
| [AtomParser::ns_to_prefix](https://developer.wordpress.org/reference/classes/atomparser/ns_to_prefix/) | – | 
| [AtomParser::parse](https://developer.wordpress.org/reference/classes/atomparser/parse/) | – | 
| [AtomParser::start_element](https://developer.wordpress.org/reference/classes/atomparser/start_element/) | – | 
| [AtomParser::start_ns](https://developer.wordpress.org/reference/classes/atomparser/start_ns/) | – | 
| [AtomParser::xml_escape](https://developer.wordpress.org/reference/classes/atomparser/xml_escape/) | – |

## 󠀁[Source](https://developer.wordpress.org/reference/classes/AtomParser/?output_format=md#source)󠁿

    ```php
    class AtomParser {

        var $NS = 'http://www.w3.org/2005/Atom';
        var $ATOM_CONTENT_ELEMENTS = array('content','summary','title','subtitle','rights');
        var $ATOM_SIMPLE_ELEMENTS = array('id','updated','published','draft');

        var $debug = false;

        var $depth = 0;
        var $indent = 2;
        var $in_content;
        var $ns_contexts = array();
        var $ns_decls = array();
        var $content_ns_decls = array();
        var $content_ns_contexts = array();
        var $is_xhtml = false;
        var $is_html = false;
        var $is_text = true;
        var $skipped_div = false;

        var $FILE = "php://input";

        var $feed;
        var $current;
        var $map_attrs_func;
        var $map_xmlns_func;
        var $error;
        var $content;

    	/**
    	 * PHP5 constructor.
    	 */
        function __construct() {

            $this->feed = new AtomFeed();
            $this->current = null;
            $this->map_attrs_func = array( __CLASS__, 'map_attrs' );
            $this->map_xmlns_func = array( __CLASS__, 'map_xmlns' );
        }

    	/**
    	 * PHP4 constructor.
    	 */
    	public function AtomParser() {
    		self::__construct();
    	}

    	/**
    	 * Map attributes to key="val"
    	 *
    	 * @param string $k Key
    	 * @param string $v Value
    	 * @return string
    	 */
    	public static function map_attrs($k, $v) {
    		return "$k=\"$v\"";
    	}

    	/**
    	 * Map XML namespace to string.
    	 *
    	 * @param indexish $p XML Namespace element index
    	 * @param array $n Two-element array pair. [ 0 => {namespace}, 1 => {url} ]
    	 * @return string 'xmlns="{url}"' or 'xmlns:{namespace}="{url}"'
    	 */
    	public static function map_xmlns($p, $n) {
    		$xd = "xmlns";
    		if( 0 < strlen($n[0]) ) {
    			$xd .= ":{$n[0]}";
    		}
    		return "{$xd}=\"{$n[1]}\"";
    	}

        function _p($msg) {
            if($this->debug) {
                print str_repeat(" ", $this->depth * $this->indent) . $msg ."\n";
            }
        }

        function error_handler($log_level, $log_text, $error_file, $error_line) {
            $this->error = $log_text;
        }

        function parse() {

            set_error_handler(array(&$this, 'error_handler'));

            array_unshift($this->ns_contexts, array());

            if ( ! function_exists( 'xml_parser_create_ns' ) ) {
            	trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );
            	return false;
            }

            $parser = xml_parser_create_ns();
            xml_set_element_handler($parser, array($this, "start_element"), array($this, "end_element"));
            xml_parser_set_option($parser,XML_OPTION_CASE_FOLDING,0);
            xml_parser_set_option($parser,XML_OPTION_SKIP_WHITE,0);
            xml_set_character_data_handler($parser, array($this, "cdata"));
            xml_set_default_handler($parser, array($this, "_default"));
            xml_set_start_namespace_decl_handler($parser, array($this, "start_ns"));
            xml_set_end_namespace_decl_handler($parser, array($this, "end_ns"));

            $this->content = '';

            $ret = true;

            $fp = fopen($this->FILE, "r");
            while ($data = fread($fp, 4096)) {
                if($this->debug) $this->content .= $data;

                if(!xml_parse($parser, $data, feof($fp))) {
                    /* translators: 1: Error message, 2: Line number. */
                    trigger_error(sprintf(__('XML Error: %1$s at line %2$s')."\n",
                        xml_error_string(xml_get_error_code($parser)),
                        xml_get_current_line_number($parser)));
                    $ret = false;
                    break;
                }
            }
            fclose($fp);

            if (PHP_VERSION_ID < 80000) { // xml_parser_free() has no effect as of PHP 8.0.
                xml_parser_free($parser);
            }

            unset($parser);

            restore_error_handler();

            return $ret;
        }

        function start_element($parser, $name, $attrs) {

            $name_parts = explode(":", $name);
            $tag        = array_pop($name_parts);

            switch($name) {
                case $this->NS . ':feed':
                    $this->current = $this->feed;
                    break;
                case $this->NS . ':entry':
                    $this->current = new AtomEntry();
                    break;
            };

            $this->_p("start_element('$name')");
            #$this->_p(print_r($this->ns_contexts,true));
            #$this->_p('current(' . $this->current . ')');

            array_unshift($this->ns_contexts, $this->ns_decls);

            $this->depth++;

            if(!empty($this->in_content)) {

                $this->content_ns_decls = array();

                if($this->is_html || $this->is_text)
                    trigger_error("Invalid content in element found. Content must not be of type text or html if it contains markup.");

                $attrs_prefix = array();

                // resolve prefixes for attributes
                foreach($attrs as $key => $value) {
                    $with_prefix = $this->ns_to_prefix($key, true);
                    $attrs_prefix[$with_prefix[1]] = $this->xml_escape($value);
                }

                $attrs_str = join(' ', array_map($this->map_attrs_func, array_keys($attrs_prefix), array_values($attrs_prefix)));
                if(strlen($attrs_str) > 0) {
                    $attrs_str = " " . $attrs_str;
                }

                $with_prefix = $this->ns_to_prefix($name);

                if(!$this->is_declared_content_ns($with_prefix[0])) {
                    array_push($this->content_ns_decls, $with_prefix[0]);
                }

                $xmlns_str = '';
                if(count($this->content_ns_decls) > 0) {
                    array_unshift($this->content_ns_contexts, $this->content_ns_decls);
                    $xmlns_str .= join(' ', array_map($this->map_xmlns_func, array_keys($this->content_ns_contexts[0]), array_values($this->content_ns_contexts[0])));
                    if(strlen($xmlns_str) > 0) {
                        $xmlns_str = " " . $xmlns_str;
                    }
                }

                array_push($this->in_content, array($tag, $this->depth, "<". $with_prefix[1] ."{$xmlns_str}{$attrs_str}" . ">"));

            } else if(in_array($tag, $this->ATOM_CONTENT_ELEMENTS) || in_array($tag, $this->ATOM_SIMPLE_ELEMENTS)) {
                $this->in_content = array();
                $this->is_xhtml = $attrs['type'] == 'xhtml';
                $this->is_html = $attrs['type'] == 'html' || $attrs['type'] == 'text/html';
                $this->is_text = !in_array('type',array_keys($attrs)) || $attrs['type'] == 'text';
                $type = $this->is_xhtml ? 'XHTML' : ($this->is_html ? 'HTML' : ($this->is_text ? 'TEXT' : $attrs['type']));

                if(in_array('src',array_keys($attrs))) {
                    $this->current->$tag = $attrs;
                } else {
                    array_push($this->in_content, array($tag,$this->depth, $type));
                }
            } else if($tag == 'link') {
                array_push($this->current->links, $attrs);
            } else if($tag == 'category') {
                array_push($this->current->categories, $attrs);
            }

            $this->ns_decls = array();
        }

        function end_element($parser, $name) {

            $name_parts = explode(":", $name);
            $tag        = array_pop($name_parts);

            $ccount = count($this->in_content);

            # if we are *in* content, then let's proceed to serialize it
            if(!empty($this->in_content)) {
                # if we are ending the original content element
                # then let's finalize the content
                if($this->in_content[0][0] == $tag &&
                    $this->in_content[0][1] == $this->depth) {
                    $origtype = $this->in_content[0][2];
                    array_shift($this->in_content);
                    $newcontent = array();
                    foreach($this->in_content as $c) {
                        if(count($c) == 3) {
                            array_push($newcontent, $c[2]);
                        } else {
                            if($this->is_xhtml || $this->is_text) {
                                array_push($newcontent, $this->xml_escape($c));
                            } else {
                                array_push($newcontent, $c);
                            }
                        }
                    }
                    if(in_array($tag, $this->ATOM_CONTENT_ELEMENTS)) {
                        $this->current->$tag = array($origtype, join('',$newcontent));
                    } else {
                        $this->current->$tag = join('',$newcontent);
                    }
                    $this->in_content = array();
                } else if($this->in_content[$ccount-1][0] == $tag &&
                    $this->in_content[$ccount-1][1] == $this->depth) {
                    $this->in_content[$ccount-1][2] = substr($this->in_content[$ccount-1][2],0,-1) . "/>";
                } else {
                    # else, just finalize the current element's content
                    $endtag = $this->ns_to_prefix($name);
                    array_push($this->in_content, array($tag, $this->depth, "</$endtag[1]>"));
                }
            }

            array_shift($this->ns_contexts);

            $this->depth--;

            if($name == ($this->NS . ':entry')) {
                array_push($this->feed->entries, $this->current);
                $this->current = null;
            }

            $this->_p("end_element('$name')");
        }

        function start_ns($parser, $prefix, $uri) {
            $this->_p("starting: " . $prefix . ":" . $uri);
            array_push($this->ns_decls, array($prefix,$uri));
        }

        function end_ns($parser, $prefix) {
            $this->_p("ending: #" . $prefix . "#");
        }

        function cdata($parser, $data) {
            $this->_p("data: #" . str_replace(array("\n"), array("\\n"), trim($data)) . "#");
            if(!empty($this->in_content)) {
                array_push($this->in_content, $data);
            }
        }

        function _default($parser, $data) {
            # when does this gets called?
        }


        function ns_to_prefix($qname, $attr=false) {
            # split 'http://www.w3.org/1999/xhtml:div' into ('http','//www.w3.org/1999/xhtml','div')
            $components = explode(":", $qname);

            # grab the last one (e.g 'div')
            $name = array_pop($components);

            if(!empty($components)) {
                # re-join back the namespace component
                $ns = join(":",$components);
                foreach($this->ns_contexts as $context) {
                    foreach($context as $mapping) {
                        if($mapping[1] == $ns && strlen($mapping[0]) > 0) {
                            return array($mapping, "$mapping[0]:$name");
                        }
                    }
                }
            }

            if($attr) {
                return array(null, $name);
            } else {
                foreach($this->ns_contexts as $context) {
                    foreach($context as $mapping) {
                        if(strlen($mapping[0]) == 0) {
                            return array($mapping, $name);
                        }
                    }
                }
            }
        }

        function is_declared_content_ns($new_mapping) {
            foreach($this->content_ns_contexts as $context) {
                foreach($context as $mapping) {
                    if($new_mapping == $mapping) {
                        return true;
                    }
                }
            }
            return false;
        }

        function xml_escape($content)
        {
                 return str_replace(array('&','"',"'",'<','>'),
                    array('&amp;','&quot;','&apos;','&lt;','&gt;'),
                    $content );
        }
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/atomlib.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/6.9.4/src/wp-includes/atomlib.php#L65)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/atomlib.php#L65-L403)

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