JsHttpRequest.php

<?php
/**
 * JsHttpRequest: PHP backend for JavaScript DHTML loader.
 * (C) Dmitry Koterov, http://en.dklab.ru
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * See http://www.gnu.org/copyleft/lesser.html
 *
 * Do not remove this comment if you want to use the script!
 * Íå óäàëÿéòå äàííûé êîììåíòàðèé, åñëè âû õîòèòå èñïîëüçîâàòü ñêðèïò!
 *
 * This backend library also supports POST requests additionally to GET.
 *
 * @author Dmitry Koterov 
 * @version 5.x $Id$
 */

class JsHttpRequest
{
    var $SCRIPT_ENCODING = "windows-1251";
    var $SCRIPT_DECODE_MODE = '';
    var $LOADER = null;
    var $ID = null;    
    var $RESULT = null;
    
    // Internal; uniq value.
    var $_uniqHash;
    // Magic number for display_error checking.
    var $_magic = 14623;
    // Previous display_errors value.
    var $_prevDisplayErrors = null;    
    // Internal: response content-type depending on loader type.
    var $_contentTypes = array(
        "script" => "text/javascript",
        "xml"    => "text/plain", // In XMLHttpRequest mode we must return text/plain - stupid Opera 8.0. :(
        "form"   => "text/html",
        ""       => "text/plain", // for unknown loader
    );
    // Internal: conversion to UTF-8 JSON cancelled because of non-ascii key.
    var $_toUtfFailed = false;
    // Internal: list of characters 128...255 (for strpbrk() ASCII check).
    var $_nonAsciiChars = '';
    // Which Unicode conversion function is available?
    var $_unicodeConvMethod = null;
    // Emergency memory buffer to be freed on memory_limit error.
    var $_emergBuffer = null;

    
    /**
     * Constructor.
     * 
     * Create new JsHttpRequest backend object and attach it
     * to script output buffer. As a result - script will always return
     * correct JavaScript code, even in case of fatal errors.
     *
     * QUERY_STRING is in form of: PHPSESSID=<sid>&a=aaa&b=bbb&JsHttpRequest=<id>-<loader>
     * where <id> is a request ID, <loader> is a loader name, <sid> - a session ID (if present), 
     * PHPSESSID - session parameter name (by default = "PHPSESSID").
     * 
     * If an object is created WITHOUT an active AJAX query, it is simply marked as
     * non-active. Use statuc method isActive() to check.
     */
    function JsHttpRequest($enc)
    {
        global $JsHttpRequest_Active;
        
        // To be on a safe side - do not allow to drop reference counter on ob processing.
        $GLOBALS['_RESULT'] =& $this->RESULT; 
        
        // Parse QUERY_STRING.
        if (preg_match('/^(.*)(?:&|^)JsHttpRequest=(?:(\d+)-)?([^&]+)((?:&|$).*)$/s', @$_SERVER['QUERY_STRING'], $m)) {
            $this->ID = $m[2];
            $this->LOADER = strtolower($m[3]);
            $_SERVER['QUERY_STRING'] = preg_replace('/^&+|&+$/s', '', preg_replace('/(^|&)'.session_name().'=[^&]*&?/s', '&', $m[1] . $m[4]));
            unset(
                $_GET['JsHttpRequest'],
                $_REQUEST['JsHttpRequest'],
                $_GET[session_name()],
                $_POST[session_name()],
                $_REQUEST[session_name()]
            );
            // Detect Unicode conversion method.
            $this->_unicodeConvMethod = function_exists('mb_convert_encoding')? 'mb' : (function_exists('iconv')? 'iconv' : null);
    
            // Fill an emergency buffer. We erase it at the first line of OB processor
            // to free some memory. This memory may be used on memory_limit error.
            $this->_emergBuffer = str_repeat('a', 1024 * 200);

            // Intercept fatal errors via display_errors (seems it is the only way).     
            $this->_uniqHash = md5('JsHttpRequest' . microtime() . getmypid());
            $this->_prevDisplayErrors = ini_get('display_errors');
            ini_set('display_errors', $this->_magic); //
            ini_set('error_prepend_string', $this->_uniqHash . ini_get('error_prepend_string'));
            ini_set('error_append_string',  ini_get('error_append_string') . $this->_uniqHash);
            if (function_exists('xdebug_disable')) xdebug_disable(); // else Fatal errors are not catched

            // Start OB handling early.
            ob_start(array(&$this, "_obHandler"));
            $JsHttpRequest_Active = true;
    
            // Set up the encoding.
            $this->setEncoding($enc);
    
            // Check if headers are already sent (see Content-Type library usage).
            // If true - generate a debug message and exit.
            $file = $line = null;
            $headersSent = version_compare(PHP_VERSION, "4.3.0") < 0? headers_sent() : headers_sent($file, $line);
            if ($headersSent) {
                trigger_error(
                    "HTTP headers are already sent" . ($line !== null? " in $file on line $line" : " somewhere in the script") . ". "
                    . "Possibly you have an extra space (or a newline) before the first line of the script or any library. "
                    . "Please note that JsHttpRequest uses its own Content-Type header and fails if "
                    . "this header cannot be set. See header() function documentation for more details",
                    E_USER_ERROR
                );
                exit();
            }
        } else {
            $this->ID = 0;
            $this->LOADER = 'unknown';
            $JsHttpRequest_Active = false;
        }
    }
    

    /**
     * Static function.
     * Returns true if JsHttpRequest output processor is currently active.
     * 
     * @return boolean    True if the library is active, false otherwise.
     */
    function isActive()
    {
        return !empty($GLOBALS['JsHttpRequest_Active']);
    }
    

    /**
     * string getJsCode()
     * 
     * Return JavaScript part of the library.
     */
    function getJsCode()
    {
        return file_get_contents(dirname(__FILE__) . '/JsHttpRequest.js');
    }


    /**
     * void setEncoding(string $encoding)
     * 
     * Set an active script encoding & correct QUERY_STRING according to it.
     * Examples:
     *   "windows-1251"          - set plain encoding (non-windows characters, 
     *                             e.g. hieroglyphs, are totally ignored)
     *   "windows-1251 entities" - set windows encoding, BUT additionally replace:
     *                             "&"         ->  "&amp;" 
     *                             hieroglyph  ->  &#XXXX; entity
     */
    function setEncoding($enc)
    {
        // Parse an encoding.
        preg_match('/^(\S*)(?:\s+(\S*))$/', $enc, $p);
        $this->SCRIPT_ENCODING    = strtolower(!empty($p[1])? $p[1] : $enc);
        $this->SCRIPT_DECODE_MODE = !empty($p[2])? $p[2] : '';
        // Manually parse QUERY_STRING because of damned Unicode's %uXXXX.
        $this->_correctSuperglobals();
    }

    
    /**
     * string quoteInput(string $input)
     * 
     * Quote a string according to the input decoding mode.
     * If entities are used (see setEncoding()), no '&' character is quoted,
     * only '"', '>' and '<' (we presume that '&' is already quoted by
     * an input reader function).
     *
     * Use this function INSTEAD of htmlspecialchars() for $_GET data 
     * in your scripts.
     */
    function quoteInput($s)
    {
        if ($this->SCRIPT_DECODE_MODE == 'entities')
            return str_replace(array('"', '<', '>'), array('&quot;', '&lt;', '&gt;'), $s);
        else
            return htmlspecialchars($s);
    }
    

    /**
     * Convert a PHP scalar, array or hash to JS scalar/array/hash. This function is 
     * an analog of json_encode(), but it can work with a non-UTF8 input and does not 
     * analyze the passed data. Output format must be fully JSON compatible.
     * 
     * @param mixed $a   Any structure to convert to JS.
     * @return string    JavaScript equivalent structure.
     */
    function php2js($a=false)
    {
        if (is_null($a)) return 'null';
        if ($a === false) return 'false';
        if ($a === true) return 'true';
        if (is_scalar($a)) {
            if (is_float($a)) {
                // Always use "." for floats.
                $a = str_replace(",", ".", strval($a));
            }
            // All scalars are converted to strings to avoid indeterminism.
            // PHP's "1" and 1 are equal for all PHP operators, but 
            // JS's "1" and 1 are not. So if we pass "1" or 1 from the PHP backend,
            // we should get the same result in the JS frontend (string).
            // Character replacements for JSON.
            static $jsonReplaces = array(
                array("\\", "/", "\n", "\t", "\r", "\b", "\f", '"'),
                array('\\\\', '\\/', '\\n', '\\t', '\\r', '\\b', '\\f', '\"')
            );
            return '"' . str_replace($jsonReplaces[0], $jsonReplaces[1], $a) . '"';
        }
        $isList = true;
        for ($i = 0, reset($a); $i < count($a); $i++, next($a)) {
            if (key($a) !== $i) { 
                $isList = false; 
                break; 
            }
        }
        $result = array();
        if ($isList) {
            foreach ($a as $v) {
                $result[] = JsHttpRequest::php2js($v);
            }
            return '[ ' . join(', ', $result) . ' ]';
        } else {
            foreach ($a as $k => $v) {
                $result[] = JsHttpRequest::php2js($k) . ': ' . JsHttpRequest::php2js($v);
            }
            return '{ ' . join(', ', $result) . ' }';
        }
    }
    
        
    /**
     * Internal methods.
     */

    /**
     * Parse & decode QUERY_STRING.
     */
    function _correctSuperglobals()
    {
        // In case of FORM loader we may go to nirvana, everything is already parsed by PHP.
        if ($this->LOADER == 'form') return;
        
        // ATTENTION!!!
        // HTTP_RAW_POST_DATA is only accessible when Content-Type of POST request
        // is NOT default "application/x-www-form-urlencoded"!!!
        // Library frontend sets "application/octet-stream" for that purpose,
        // see JavaScript code. In PHP 5.2.2.HTTP_RAW_POST_DATA is not set sometimes; 
        // in such cases - read the POST data manually from the STDIN stream.
        $rawPost = strcasecmp($_SERVER['REQUEST_METHOD'], 'POST') == 0? (isset($GLOBALS['HTTP_RAW_POST_DATA'])? $GLOBALS['HTTP_RAW_POST_DATA'] : @file_get_contents("php://input")) : null;
        $source = array(
            '_GET' => !empty($_SERVER['QUERY_STRING'])? $_SERVER['QUERY_STRING'] : null, 
            '_POST'=> $rawPost,
        );
        foreach ($source as $dst=>$src) {
            // First correct all 2-byte entities.
            $s = preg_replace('/%(?!5B)(?!5D)([0-9a-f]{2})/si', '%u00\\1', $src);
            // Now we can use standard parse_str() with no worry!
            $data = null;
            parse_str($s, $data);
            $GLOBALS[$dst] = $this->_ucs2EntitiesDecode($data);
        }
        $GLOBALS['HTTP_GET_VARS'] = $_GET; // deprecated vars
        $GLOBALS['HTTP_POST_VARS'] = $_POST;
        $_REQUEST = 
            (isset($_COOKIE)? $_COOKIE : array()) + 
            (isset($_POST)? $_POST : array()) + 
            (isset($_GET)? $_GET : array());
        if (ini_get('register_globals')) {
            // TODO?
        }
    }


    /**
     * Called in case of error too!
     */
    function _obHandler($text)
    {
        unset($this->_emergBuffer); // free a piece of memory for memory_limit error
        unset($GLOBALS['JsHttpRequest_Active']);
        
        // Check for error & fetch a resulting data.
        $wasFatalError = false;
        if (preg_match_all("/{$this->_uniqHash}(.*?){$this->_uniqHash}/sx", $text, $m)) {
            // Display_errors:
            // 1. disabled manually after the library initialization, or
            // 2. was initially disabled and is not changed
            $needRemoveErrorMessages = !ini_get('display_errors') || (!$this->_prevDisplayErrors && ini_get('display_errors') == $this->_magic);
            foreach ($m[0] as $error) {
                if (preg_match('/\bFatal error(<.*?>)?:/i', $error)) {
                    $wasFatalError = true;
                }
                if ($needRemoveErrorMessages) {
                    $text = str_replace($error, '', $text); // strip the whole error message
                } else {
                    $text = str_replace($this->_uniqHash, '', $text);
                }
            }
        }
        if ($wasFatalError) {
            // On fatal errors - force "null" result. This is needed, because $_RESULT
            // may not be fully completed at the moment of the error.
            $this->RESULT = null;
        } else {
            // Read the result from globals if not set directly.
            if (!isset($this->RESULT)) {
                global $_RESULT;
                $this->RESULT = $_RESULT;
            }
            // Avoid manual NULLs in the result (very important!).
            if ($this->RESULT === null) {
                $this->RESULT = false;
            }
        }
        
        // Note that 500 error is generated when a PHP error occurred.
        $status = $this->RESULT === null? 500 : 200;
        $result = array(
            'id'   => $this->ID,
            'js'   => $this->RESULT,  // null always means a fatal error...
            'text' => $text,          // ...independent on $text!!!
        );
        $encoding = $this->SCRIPT_ENCODING;
        $text = null; // to be on a safe side
        
        // Try to use very fast json_encode: 3-4 times faster than a manual encoding.
        if (function_exists('array_walk_recursive') && function_exists('json_encode') && $this->_unicodeConvMethod) {
            $this->_nonAsciiChars = join("", array_map('chr', range(128, 255)));
            $this->_toUtfFailed = false;
            $resultUtf8 = $result;
            array_walk_recursive($resultUtf8, array(&$this, '_toUtf8_callback'), $this->SCRIPT_ENCODING);
            if (!$this->_toUtfFailed) {
                // If some key contains non-ASCII character, convert everything manually.
                $text = json_encode($resultUtf8);
                $encoding = "UTF-8";
            }
        }
        
        // On failure, use manual encoding.
        if ($text === null) {
            $text = $this->php2js($result);
        }

        if ($this->LOADER != "xml") {
            // In non-XML mode we cannot use plain JSON. So - wrap with JS function call.
            // If top.JsHttpRequestGlobal is not defined, loading is aborted and 
            // iframe is removed, so - do not call dataReady().
            $text = "" 
                . ($this->LOADER == "form"? 'top && top.JsHttpRequestGlobal && top.JsHttpRequestGlobal' : 'JsHttpRequest') 
                . ".dataReady(" . $text . ")\n"
                . "";
            if ($this->LOADER == "form") {
                $text = '<script type="text/javascript" language="JavaScript"><!--' . "\n$text" . '//--></script>';
            }
            
            // Always return 200 code in non-XML mode (else SCRIPT does not work in FF).
            // For XML mode, 500 code is okay.
            $status = 200;
        }

        // Status header. To be safe, display it only in error mode. In case of success 
        // termination, do not modify the status (""HTTP/1.1 ..." header seems to be not
        // too cross-platform).
        if ($this->RESULT === null) {
            if (php_sapi_name() == "cgi") {
                header("Status: $status");
            } else {
                header("HTTP/1.1 $status");
            }
        }

        // In XMLHttpRequest mode we must return text/plain - damned stupid Opera 8.0. :(
        $ctype = !empty($this->_contentTypes[$this->LOADER])? $this->_contentTypes[$this->LOADER] : $this->_contentTypes[''];
        header("Content-type: $ctype; charset=$encoding");

        return $text;
    }


    /**
     * Internal function, used in array_walk_recursive() before json_encode() call.
     * If a key contains non-ASCII characters, this function sets $this->_toUtfFailed = true,
     * becaues array_walk_recursive() cannot modify array keys.
     */
    function _toUtf8_callback(&$v, $k, $fromEnc)
    {
        if ($v === null || is_bool($v)) return;
        if ($this->_toUtfFailed || !is_scalar($v) || strpbrk($k, $this->_nonAsciiChars) !== false) {
            $this->_toUtfFailed = true;
        } else {
            $v = $this->_unicodeConv($fromEnc, 'UTF-8', $v);
        }
    }
    

    /**
     * Decode all %uXXXX entities in string or array (recurrent).
     * String must not contain %XX entities - they are ignored!
     */
    function _ucs2EntitiesDecode($data)
    {
        if (is_array($data)) {
            $d = array();
            foreach ($data as $k=>$v) {
                $d[$this->_ucs2EntitiesDecode($k)] = $this->_ucs2EntitiesDecode($v);
            }
            return $d;
        } else {
            if (strpos($data, '%u') !== false) { // improve speed
                $data = preg_replace_callback('/%u([0-9A-F]{1,4})/si', array(&$this, '_ucs2EntitiesDecodeCallback'), $data);
            }
            return $data;
        }
    }


    /**
     * Decode one %uXXXX entity (RE callback).
     */
    function _ucs2EntitiesDecodeCallback($p)
    {
        $hex = $p[1];
        $dec = hexdec($hex);
        if ($dec === "38" && $this->SCRIPT_DECODE_MODE == 'entities') {
            // Process "&" separately in "entities" decode mode.
            $c = "&amp;";
        } else {
            if ($this->_unicodeConvMethod) {
                $c = @$this->_unicodeConv('UCS-2BE', $this->SCRIPT_ENCODING, pack('n', $dec));
            } else {
                $c = $this->_decUcs2Decode($dec, $this->SCRIPT_ENCODING);
            }
            if (!strlen($c)) {
                if ($this->SCRIPT_DECODE_MODE == 'entities') {
                    $c = '&#' . $dec . ';';
                } else {
                    $c = '?';
                }
            }
        }
        return $c;
    }


    /**
     * Wrapper for iconv() or mb_convert_encoding() functions.
     * This function will generate fatal error if none of these functons available!
     * 
     * @see iconv()
     */
    function _unicodeConv($fromEnc, $toEnc, $v)
    {
        if ($this->_unicodeConvMethod == 'iconv') {
            return iconv($fromEnc, $toEnc, $v);
        } 
        return mb_convert_encoding($v, $toEnc, $fromEnc);
    }


    /**
     * If there is no ICONV, try to decode 1-byte characters and UTF-8 manually
     * (for most popular charsets only).
     */
     
    /**
     * Convert from UCS-2BE decimal to $toEnc.
     */
    function _decUcs2Decode($code, $toEnc)
    {
        // Little speedup by using array_flip($this->_encTables) and later hash access.
        static $flippedTable = null;
        if ($code < 128) return chr($code);
        
        if (isset($this->_encTables[$toEnc])) {
            if (!$flippedTable) $flippedTable = array_flip($this->_encTables[$toEnc]);
            if (isset($flippedTable[$code])) return chr(128 + $flippedTable[$code]);
        } else if ($toEnc == 'utf-8' || $toEnc == 'utf8') {
            // UTF-8 conversion rules: http://www.cl.cam.ac.uk/~mgk25/unicode.html
            if ($code < 0x800) {
                return chr(0xC0 + ($code >> 6)) . 
                       chr(0x80 + ($code & 0x3F));
            } else { // if ($code <= 0xFFFF) -- it is almost always so for UCS2-BE
                return chr(0xE0 + ($code >> 12)) .
                       chr(0x80 + (0x3F & ($code >> 6))) .
                       chr(0x80 + ($code & 0x3F));
            }
        }
        
        return "";
    }
    

    /**
     * UCS-2BE -> 1-byte encodings (from #128).
     */
    var $_encTables = array(
        'windows-1251' => array(
            0x0402, 0x0403, 0x201A, 0x0453, 0x201E, 0x2026, 0x2020, 0x2021,
            0x20AC, 0x2030, 0x0409, 0x2039, 0x040A, 0x040C, 0x040B, 0x040F,
            0x0452, 0x2018, 0x2019, 0x201C, 0x201D, 0x2022, 0x2013, 0x2014,
            0x0098, 0x2122, 0x0459, 0x203A, 0x045A, 0x045C, 0x045B, 0x045F,
            0x00A0, 0x040E, 0x045E, 0x0408, 0x00A4, 0x0490, 0x00A6, 0x00A7,
            0x0401, 0x00A9, 0x0404, 0x00AB, 0x00AC, 0x00AD, 0x00AE, 0x0407,
            0x00B0, 0x00B1, 0x0406, 0x0456, 0x0491, 0x00B5, 0x00B6, 0x00B7,
            0x0451, 0x2116, 0x0454, 0x00BB, 0x0458, 0x0405, 0x0455, 0x0457,
            0x0410, 0x0411, 0x0412, 0x0413, 0x0414, 0x0415, 0x0416, 0x0417,
            0x0418, 0x0419, 0x041A, 0x041B, 0x041C, 0x041D, 0x041E, 0x041F,
            0x0420, 0x0421, 0x0422, 0x0423, 0x0424, 0x0425, 0x0426, 0x0427,
            0x0428, 0x0429, 0x042A, 0x042B, 0x042C, 0x042D, 0x042E, 0x042F,
            0x0430, 0x0431, 0x0432, 0x0433, 0x0434, 0x0435, 0x0436, 0x0437,
            0x0438, 0x0439, 0x043A, 0x043B, 0x043C, 0x043D, 0x043E, 0x043F,
            0x0440, 0x0441, 0x0442, 0x0443, 0x0444, 0x0445, 0x0446, 0x0447,
            0x0448, 0x0449, 0x044A, 0x044B, 0x044C, 0x044D, 0x044E, 0x044F,
        ),
        'koi8-r' => array(
            0x2500, 0x2502, 0x250C, 0x2510, 0x2514, 0x2518, 0x251C, 0x2524,
            0x252C, 0x2534, 0x253C, 0x2580, 0x2584, 0x2588, 0x258C, 0x2590,
            0x2591, 0x2592, 0x2593, 0x2320, 0x25A0, 0x2219, 0x221A, 0x2248,
            0x2264, 0x2265, 0x00A0, 0x2321, 0x00B0, 0x00B2, 0x00B7, 0x00F7,
            0x2550, 0x2551, 0x2552, 0x0451, 0x2553, 0x2554, 0x2555, 0x2556,
            0x2557, 0x2558, 0x2559, 0x255A, 0x255B, 0x255C, 0x255d, 0x255E,
            0x255F, 0x2560, 0x2561, 0x0401, 0x2562, 0x2563, 0x2564, 0x2565,
            0x2566, 0x2567, 0x2568, 0x2569, 0x256A, 0x256B, 0x256C, 0x00A9,
            0x044E, 0x0430, 0x0431, 0x0446, 0x0434, 0x0435, 0x0444, 0x0433,
            0x0445, 0x0438, 0x0439, 0x043A, 0x043B, 0x043C, 0x043d, 0x043E,
            0x043F, 0x044F, 0x0440, 0x0441, 0x0442, 0x0443, 0x0436, 0x0432,
            0x044C, 0x044B, 0x0437, 0x0448, 0x044d, 0x0449, 0x0447, 0x044A,
            0x042E, 0x0410, 0x0411, 0x0426, 0x0414, 0x0415, 0x0424, 0x0413,
            0x0425, 0x0418, 0x0419, 0x041A, 0x041B, 0x041C, 0x041d, 0x041E,
            0x041F, 0x042F, 0x0420, 0x0421, 0x0422, 0x0423, 0x0416, 0x0412,
            0x042C, 0x042B, 0x0417, 0x0428, 0x042d, 0x0429, 0x0427, 0x042A      
        ),
    );
}