Description:
------------
To integrate the documentation about the tidy class, here is what I found so far by testing with actual code; please consider for a possible merge with the current documentation as there are several detailed annotations:

class tidy {

	/**
	 * Informational, warning and error messages collected while parsing.
	 * Lines are separated by '\r\n'; a trailing '\r' is also added for some
	 * reason. The NULL value means either no parsing has still being performed
	 * or the parsing succeeded.
	 * @var string 
	 */
	public $errorBuffer;

	/**
	 * Initializes a new parser and possibly also parse the specified file.
	 * Hint: to parse a string, do not specify any argument and then use the
	 * parseString() method instead.
	 * @param string $filename File to parse. If this argument is provided, it
	 * must be a valid existing file name.
	 * @param mixed $config String of the configuration options or associative
	 * array of the options. Set the empty array here if you want to set the
	 * following arguments too.
	 * @param string $encoding Encoding for input and output documents.
	 * Note that the tidy library still can't parse a possible HTML META element
	 * specifying the encoding, so setting this argument is advised.
	 * Default input encoding: unspecified, possibly unexpected.
	 * Default output encoding: UTF8.
	 * BEWARE: "UTF-8" is not a recognized encoding; "UTF8" is the right spelling.
	 * @param boolean $use_include_path If true, a relative $filename path is
	 * resolved first against the directories listed in the include_path php.ini
	 * directive, and then search in the current directory. Default: FALSE.
	 * @return void
	 * @triggers E_WARNING Failed reading $filename. Failed reading the $config
	 * file when this argument is a string. Invalid $encoding.
	 * @triggers E_NOTICE Unknown or invalid $config when this argument is an
	 * associative array.
	 */
	function __construct($filename = NULL, $config = NULL, $encoding = NULL,
			$use_include_path = FALSE){}

	/**
	 * Returns the node starting with the BODY element.
	 * @return tidyNode The BODY element, either parsed or added by this library.
	 * Returns NULL if still no parsing performed.
	 */
	function body(){}
	

	// Other methods: cleanRepair(), diagnose(), getConfig(), getHtmlVer()

	/**
	 * Returns the value of the specified option.
	 * @param string $option Name of the option to retrieve.
	 * @return mixed Value of the option.
	 * @triggers E_WARNING No this option.
	 */
	function getOpt(/*. string .*/ $option){}
	
	/**
	 * Returns the documentation for the given option name.
	 * @param string $optname
	 * @return string
	 * @deprecated This method is not available; tested with getRelease() gives 2017/03/01
	 * on Wamp Server with PHP 7.1.9.
	 */
	function getOptDoc($optname){}
	
	/**
	 * Return the release date of the tidy library.
	 * @return string
	 */
	function getRelease(){}
	
	/**
	 * Returns the status of the document.
	 * @return int
	 */
	function getStatus(){}
	
	/**
	 * Returns the HEAD element.
	 * @return tidyNode The HEAD element, or NULL if not available.
	 */
	function head(){}
	
	/**
	 * Returns the HTML element.
	 * @return tidyNode The HTML element, or NULL if not available.
	 */
	function html(){}
	
	/**
	 * Tells if the document is XHTML.
	 * @return boolean
	 */
	function isXhtml(){}
	
	/**
	 * Tells if the document is XML.
	 * @return boolean
	 */
	function isXml(){}
	
	/**
	 * Parse the given file.
	 * @param string $filename File to parse.
	 * @param mixed $config String of the configuration options or associative
	 * array of the options. Set the empty array here if you want to set the
	 * following arguments too.
	 * @param string $encoding Encoding for input and output documents.
	 * Note that the tidy library still can't parse a possible HTML META element
	 * specifying the encoding, so setting this argument is advised.
	 * Default input encoding: unspecified, possibly unexpected.
	 * Default output encoding: UTF-8.
	 * BEWARE: "UTF-8" is not a recognized encoding; "UTF8" is the right spelling.
	 * @param boolean $use_include_path If true, a relative $filename path is
	 * resolved first against the directories listed in the include_path php.ini
	 * directive, and then search in the current directory. Default: FALSE.
	 * @return boolean Always returns TRUE.
	 * @triggers E_WARNING Failed reading $filename. Failed reading the $config
	 * file when this argument is a string. Invalid $encoding.
	 * @triggers E_NOTICE Unknown or invalid $config when this argument is an
	 * associative array.
	 */
	function parseFile($filename, $config = NULL, $encoding = NULL, $use_include_path = FALSE){}
	
	/**
	 * Parse the given string.
	 * @param string $input Text to parse.
	 * @param mixed $config String of the configuration options or associative
	 * array of the options. Set the empty array here if you want to set the
	 * following arguments too.
	 * @param string $encoding Encoding for input and output documents.
	 * Note that the tidy library still can't parse a possible HTML META element
	 * specifying the encoding, so setting this argument is advised.
	 * Default input encoding: unspecified, possibly unexpected.
	 * Default output encoding: UTF-8.
	 * BEWARE: "UTF-8" is not a recognized encoding; "UTF8" is the right spelling.
	 * @return boolean Always returns TRUE.
	 * @triggers E_WARNING Failed reading the $config file when this argument is
	 * a string. Invalid $encoding.
	 * @triggers E_NOTICE Unknown or invalid $config when this argument is an
	 * associative array.
	 */
	function parseString($input, $config = NULL, $encoding = NULL){}
	
	/**
	 * Parse the given file and returns the repaired result.
	 * @param string $filename File to parse. If this argument is provided, it
	 * must be a valid existing file name.
	 * @param mixed $config String of the configuration options or associative
	 * array of the options. Set the empty array here if you want to set the
	 * following arguments too.
	 * @param string $encoding Encoding for input and output documents.
	 * Note that the tidy library still can't parse a possible HTML META element
	 * specifying the encoding, so setting this argument is advised.
	 * Default input encoding: unspecified, possibly unexpected.
	 * Default output encoding: UTF-8.
	 * BEWARE: "UTF-8" is not a recognized encoding; "UTF8" is the right spelling.
	 * @param boolean $use_include_path If true, a relative $filename path is
	 * resolved first against the directories listed in the include_path php.ini
	 * directive, and then search in the current directory. Default: FALSE.
	 * @return string Repaired contents of the file.
	 * @triggers E_WARNING Failed reading $filename. Failed reading the $config
	 * file when this argument is a string. Invalid $encoding.
	 * @triggers E_NOTICE Unknown or invalid $config when this argument is an
	 * associative array.
	 */
	function repairFile($filename, $config = NULL, $encoding = NULL, $use_include_path = FALSE){}
	
	/**
	 * Parse the given string and returns the repaired result.
	 * @param string $input Text to parse.
	 * @param mixed $config String of the configuration options or associative
	 * array of the options. Set the empty array here if you want to set the
	 * following arguments too.
	 * @param string $encoding Encoding for input and output documents.
	 * Note that the tidy library still can't parse a possible HTML META element
	 * specifying the encoding, so setting this argument is advised.
	 * Default input encoding: unspecified, possibly unexpected.
	 * Default output encoding: UTF-8.
	 * BEWARE: "UTF-8" is not a recognized encoding; "UTF8" is the right spelling.
	 * @return string Repaired contents of the string.
	 * @triggers E_WARNING Failed reading the $config file when this argument is
	 * a string. Invalid $encoding.
	 * @triggers E_NOTICE Unknown or invalid $config when this argument is an
	 * associative array.
	 */
	function repairString($input, $config = NULL, $encoding = NULL){}
	
	/**
	 * Returns the root node of the parsed tree.
	 * @return tidyNode Root note of the parsed tree, possibly a tidyNode with
	 * empty name property if nothing has been parsed yet.
	 */
	function root(){}
}