1 | <?php |
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2 | /** |
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3 | * SessionCache.inc.php |
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4 | * Provides an API for storing a limited amount of data |
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5 | * intended to have a short lifetime in a user's session. |
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6 | * |
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7 | * Code by Strangecode :: www.strangecode.com :: This document contains copyrighted information. |
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8 | * @author Quinn Comendant <quinn@strangecode.com> |
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9 | * @version 1.2 |
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10 | * @since 2001 |
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11 | */ |
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12 | class SessionCache |
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13 | { |
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14 | var $_params = array( |
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15 | 'soft_limit' => 204800, |
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16 | 'hard_limit' => 4194304, |
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17 | 'min_items' => 3, |
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18 | ); |
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19 | |
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20 | /** |
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21 | * This method enforces the singleton pattern for this class. |
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22 | * |
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23 | * @return object Reference to the global SessionCache object. |
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24 | * @access public |
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25 | * @static |
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26 | */ |
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27 | function &getInstance() { |
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28 | static $instance = null; |
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29 | |
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30 | if ($instance === null) { |
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31 | $instance = new SessionCache(); |
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32 | } |
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33 | |
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34 | return $instance; |
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35 | } |
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36 | |
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37 | /** |
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38 | * Set (or overwrite existing) parameters by passing an array of new parameters. |
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39 | * |
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40 | * @access public |
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41 | * @param array $params Array of parameters (key => val pairs). |
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42 | */ |
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43 | function setParam($params) |
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44 | { |
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45 | if (isset($params) && is_array($params)) { |
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46 | // Merge new parameters with old overriding only those passed. |
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47 | $this->_params = array_merge($this->_params, $params); |
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48 | } else { |
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49 | App::logMsg(sprintf('Parameters are not an array: %s', $params), LOG_ERR, __FILE__, __LINE__); |
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50 | } |
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51 | } |
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52 | |
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53 | /** |
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54 | * Return the value of a parameter, if it exists. |
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55 | * |
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56 | * @access public |
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57 | * @param string $param Which parameter to return. |
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58 | * @return mixed Configured parameter value. |
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59 | */ |
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60 | function getParam($param) |
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61 | { |
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62 | if (isset($this->_params[$param])) { |
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63 | return $this->_params[$param]; |
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64 | } else { |
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65 | App::logMsg(sprintf('Parameter is not set: %s', $param), LOG_DEBUG, __FILE__, __LINE__); |
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66 | return null; |
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67 | } |
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68 | } |
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69 | |
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70 | /** |
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71 | * Stores a new variable in the session cache. The $var_id is is md5'ed |
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72 | * because if a variable id is a very large integer, the array_shift function |
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73 | * will reset the key to the next largest int key. Weird behaviour I can't |
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74 | * understand. $session_cache[32341234123] will become $session_cache[0] |
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75 | * for example. Usage warning: if the variable is too big to fit, or is |
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76 | * old and discarded, you must provide alternative ways of accessing the data. |
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77 | * |
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78 | * @param mixed $var The var to store in the session cache. |
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79 | * @param str $var_id An identifyer for the cached object. |
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80 | * @param bool $force_it_in If we have something really big that we |
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81 | * still want to cache, setting this true |
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82 | * allows this. |
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83 | * |
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84 | * @return string The $var_id, or false if the object was too big to cache. |
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85 | */ |
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86 | function putCache($var, $var_id, $force_it_in=false) |
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87 | { |
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88 | $cache =& SessionCache::getInstance(); |
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89 | |
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90 | $var_id = md5($var_id); |
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91 | $serialized_var = serialize($var); |
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92 | $serialized_var_len = strlen($serialized_var); |
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93 | |
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94 | if ($serialized_var_len >= $cache->getParam('soft_limit') && !$force_it_in) { |
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95 | App::logMsg(sprintf('Serialized variable (%s bytes) more than soft_limit (%s bytes).', $serialized_var_len, $cache->getParam('soft_limit')), LOG_NOTICE, __FILE__, __LINE__); |
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96 | return false; |
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97 | } |
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98 | |
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99 | if ($serialized_var_len >= $cache->getParam('hard_limit')) { |
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100 | App::logMsg(sprintf('Serialized variable (%s bytes) more than hard_limit (%s bytes).', $serialized_var_len, $cache->getParam('hard_limit')), LOG_NOTICE, __FILE__, __LINE__); |
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101 | return false; |
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102 | } |
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103 | |
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104 | if (!isset($_SESSION['_session_cache'])) { |
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105 | $_SESSION['_session_cache'] = array(); |
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106 | } else { |
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107 | unset($_SESSION['_session_cache'][$var_id]); |
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108 | // Continue to prune the cache if it's length is too long for the new variable to fit, but keep at least MIN_ITEMS at least. |
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109 | while (strlen(serialize($_SESSION['_session_cache'])) + $serialized_var_len >= $cache->getParam('soft_limit') |
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110 | && sizeof($_SESSION['_session_cache']) >= $cache->getParam('min_items')) { |
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111 | array_shift($_SESSION['_session_cache']); |
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112 | } |
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113 | } |
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114 | $_SESSION['_session_cache'][$var_id] =& $serialized_var; |
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115 | |
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116 | if ($serialized_var_len >= 1024000) { |
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117 | App::logMsg(sprintf('Successfully cached oversized variable (%s bytes).', $serialized_var_len), LOG_DEBUG, __FILE__, __LINE__); |
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118 | } |
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119 | |
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120 | return $var_id; |
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121 | } |
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122 | |
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123 | /** |
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124 | * Retrives an object from the session cache and returns it unserialized. |
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125 | * It also moves it to the top of the stack, which makes it such that the |
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126 | * cache flushing mechanism of putCache deletes the oldest referenced items |
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127 | * first. |
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128 | * |
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129 | * @param string $var_id The identifyer for the datum to retrieve. |
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130 | * |
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131 | * @return mixed The requested datum, or false on failure. |
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132 | */ |
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133 | function getCache($var_id) |
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134 | { |
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135 | $var_id = md5($var_id); |
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136 | if (isset($_SESSION['_session_cache'][$var_id])) { |
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137 | // Move the accessed cached datum to the top of the stack. Maybe somebody knows a better way to do this? |
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138 | $tmp =& $_SESSION['_session_cache'][$var_id]; |
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139 | unset($_SESSION['_session_cache'][$var_id]); |
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140 | $_SESSION['_session_cache'][$var_id] =& $tmp; |
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141 | // Return the unserialized datum. |
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142 | return unserialize($_SESSION['_session_cache'][$var_id]); |
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143 | } else { |
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144 | return false; |
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145 | } |
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146 | } |
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147 | |
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148 | /** |
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149 | * Tells you if the object is cached. |
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150 | * |
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151 | * @param string $var_id The ID of the object to check. |
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152 | * |
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153 | * @return bool The return from isset(). |
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154 | */ |
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155 | function isCached($var_id) |
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156 | { |
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157 | $var_id = md5($var_id); |
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158 | return isset($_SESSION['_session_cache'][$var_id]); |
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159 | } |
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160 | |
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161 | /** |
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162 | * Tells you if the object is cached. |
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163 | * |
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164 | * @param string $var_id The ID of the object to check. |
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165 | * |
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166 | * @return bool The return from isset(). |
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167 | */ |
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168 | function breakCache($var_id) |
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169 | { |
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170 | $var_id = md5($var_id); |
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171 | if (isset($_SESSION['_session_cache'][$var_id])) { |
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172 | unset($_SESSION['_session_cache'][$var_id]); |
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173 | } |
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174 | } |
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175 | |
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176 | // END SessionCache |
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177 | } |
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178 | |
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179 | ?> |
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