qcubed/framework

<?php
    /**
     * Session-based FormState handler.  Uses PHP Sessions to store the form state.
     * 
     * Stores the variables in the following format:
     * $_SESSION['qformstate'][form_uniquid][state#]
     *   where the form_uniquid is a unique id that sticks with the window that the
     *   form is on, and state# is the formstate associated with that window. Multiple
     *   formstates need to be saved to support the browser back button.
     * 
     * If requested by QForm, the index will be encrypted.
     * 
     * This incorporates a system of garbage collection that will allow for at most BackButtonMax
     * formstates to be saved in the session.
     *
     * This handler is compatible with asynchronous ajax calls.
     *
     */
    class QSessionFormStateHandler extends QBaseClass {
        
        public static $BackButtonMax = 20; // maximum number of back button states we remember
        
        public static function Save($strFormState, $blnBackButtonFlag) {
            // Compress (if available)
            if (function_exists('gzcompress'))
                $strFormState = gzcompress($strFormState, 9);
                
            if (empty($_POST['Qform__FormState'])) {
                // no prior form state, so create a new one.
                $strFormInstance = uniqid();
                $intFormStateIndex = 1;
            } else {
                $strPriorState = $_POST['Qform__FormState'];
                
                if (!is_null(QForm::$EncryptionKey)) {
                    // Use QCryptography to Decrypt
                    $objCrypto = new QCryptography(QForm::$EncryptionKey, true);
                    $strPriorState = $objCrypto->Decrypt($strPriorState);
                }
                
                $a = explode ('_', $strPriorState);
                if (count ($a) == 2 && 
                        is_numeric ($a[1]) &&
                        !empty($_SESSION['qformstate'][$a[0]]['index'])) {
                    $strFormInstance = $a[0];
                    $intFormStateIndex = $_SESSION['qformstate'][$a[0]]['index'];
                    if ($blnBackButtonFlag) { // can we reuse current state info?
                        $intFormStateIndex ++; // nope
                        
                        // try to garbage collect
                        if (count($_SESSION['qformstate'][$a[0]]) > self::$BackButtonMax) {
                            foreach ($_SESSION['qformstate'][$a[0]] as $key=>$val) {
                                if (is_numeric($key) && $key < $_SESSION['qformstate'][$a[0]]['index'] - self::$BackButtonMax) {
                                    unset ($_SESSION['qformstate'][$a[0]][$key]);
                                }
                            }
                        }
                    }
                } else {
                    // couldn't find old session variables, so create new one
                    $strFormInstance = uniqid();
                    $intFormStateIndex = 1;
                }
            }
                
            // Setup current state variable
            if (empty($_SESSION['qformstate'])) {
                $_SESSION['qformstate'] = array();
            } 
            if (empty($_SESSION['qformstate'][$strFormInstance])) {
                $_SESSION['qformstate'][$strFormInstance] = array();
            } 
            
            $_SESSION['qformstate'][$strFormInstance]['index'] = $intFormStateIndex;
            $_SESSION['qformstate'][$strFormInstance][$intFormStateIndex] = $strFormState;
            
            $strPostDataState = $strFormInstance . '_' . $intFormStateIndex;
            
            // Return StateIndex
            if (!is_null(QForm::$EncryptionKey)) {
                // Use QCryptography to Encrypt
                $objCrypto = new QCryptography(QForm::$EncryptionKey, true);
                return $objCrypto->Encrypt($strPostDataState);
            } else
                return $strPostDataState;
        }

        public static function Load($strPostDataState) {
            // Pull Out intStateIndex
            if (!is_null(QForm::$EncryptionKey)) {
                // Use QCryptography to Decrypt
                $objCrypto = new QCryptography(QForm::$EncryptionKey, true);
                $strPostDataState = $objCrypto->Decrypt($strPostDataState);
            }
        
            $a = explode ('_', $strPostDataState);
            if (count ($a) == 2 && 
                    is_numeric ($a[1]) &&
                    !empty($_SESSION['qformstate'][$a[0]][$a[1]])) {
                $strSerializedForm = $_SESSION['qformstate'][$a[0]][$a[1]];
            } else {
                return null;
            }
            
            // Uncompress (if available)
            // NOTE: if gzcompress is used, we are restoring the *BINARY* data stream of the compressed formstate
            // In theory, this SHOULD work.  But if there is a webserver/os/php version that doesn't like
            // binary session streams, you can first base64_decode before restoring from session (see note above).
            if (function_exists('gzcompress')) {
                $strSerializedForm = gzuncompress($strSerializedForm);
            }

            return $strSerializedForm;
        }
    }