1 | <?php |
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2 | /** |
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3 | * Cache.inc.php |
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4 | * code by strangecode :: www.strangecode.com :: this document contains copyrighted information |
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5 | * |
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6 | * Provides an API for storing a limited amount of data |
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7 | * intended to have a short lifetime in a user's session. |
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8 | * |
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9 | * @author Quinn Comendant <quinn@strangecode.com> |
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10 | * @version 2.1 |
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11 | * @since 2001 |
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12 | */ |
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13 | |
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14 | // Flags. |
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15 | define('CACHE_ALLOW_OVERSIZED', 1); |
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16 | |
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17 | class Cache { |
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18 | |
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19 | // Namespace of this instance of Prefs. |
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20 | var $_ns; |
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21 | |
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22 | // Configuration parameters for this object. |
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23 | var $_params = array( |
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24 | |
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25 | // If false nothing will be cached or retreived. Useful for testing realtime data requests. |
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26 | 'enabled' => true, |
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27 | |
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28 | // The maximum size in bytes of any one variable. |
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29 | 'item_size_limit' => 4194304, // 4 MB |
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30 | |
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31 | // The maximum size in bytes before the cache will begin flushing out old items. |
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32 | 'stack_size_limit' => 4194304, // 4 MB |
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33 | |
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34 | // The minimum items to keep in the cache regardless of item or cache size. |
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35 | 'min_items' => 5, |
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36 | ); |
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37 | |
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38 | /* |
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39 | * Constructor |
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40 | * |
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41 | * @access public |
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42 | * @param string $namespace This object will store data under this realm. |
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43 | * @author Quinn Comendant <quinn@strangecode.com> |
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44 | * @version 1.0 |
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45 | * @since 05 Jun 2006 23:14:21 |
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46 | */ |
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47 | function Cache($namespace='') |
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48 | { |
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49 | $app =& App::getInstance(); |
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50 | |
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51 | $this->_ns = $namespace; |
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52 | |
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53 | if (true !== $app->getParam('enable_session')) { |
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54 | $app->logMsg('Cache disabled, enable_session is false.', LOG_INFO, __FILE__, __LINE__); |
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55 | $this->setParam(array('enabled' => false)); |
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56 | } |
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57 | |
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58 | if (!isset($_SESSION['_cache'][$this->_ns])) { |
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59 | $this->clear(); |
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60 | } |
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61 | } |
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62 | |
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63 | /** |
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64 | * This method enforces the singleton pattern for this class. |
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65 | * |
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66 | * @return object Reference to the global Cache object. |
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67 | * @access public |
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68 | * @static |
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69 | */ |
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70 | function &getInstance($namespace='') |
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71 | { |
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72 | static $instances = array(); |
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73 | |
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74 | if (!array_key_exists($namespace, $instances)) { |
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75 | $instances[$namespace] = new Cache($namespace); |
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76 | } |
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77 | |
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78 | return $instances[$namespace]; |
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79 | } |
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80 | |
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81 | /** |
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82 | * Set (or overwrite existing) parameters by passing an array of new parameters. |
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83 | * |
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84 | * @access public |
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85 | * @param array $params Array of parameters (key => val pairs). |
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86 | */ |
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87 | function setParam($params) |
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88 | { |
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89 | $app =& App::getInstance(); |
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90 | |
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91 | if (isset($params) && is_array($params)) { |
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92 | // Merge new parameters with old overriding only those passed. |
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93 | $this->_params = array_merge($this->_params, $params); |
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94 | } else { |
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95 | $app->logMsg(sprintf('Parameters are not an array: %s', $params), LOG_ERR, __FILE__, __LINE__); |
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96 | } |
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97 | } |
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98 | |
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99 | /** |
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100 | * Return the value of a parameter, if it exists. |
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101 | * |
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102 | * @access public |
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103 | * @param string $param Which parameter to return. |
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104 | * @return mixed Configured parameter value. |
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105 | */ |
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106 | function getParam($param) |
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107 | { |
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108 | $app =& App::getInstance(); |
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109 | |
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110 | if (isset($this->_params[$param])) { |
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111 | return $this->_params[$param]; |
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112 | } else { |
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113 | $app->logMsg(sprintf('Parameter is not set: %s', $param), LOG_DEBUG, __FILE__, __LINE__); |
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114 | return null; |
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115 | } |
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116 | } |
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117 | |
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118 | /** |
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119 | * Stores a new variable in the session cache. The $key should not be numberic |
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120 | * because the array_shift function will reset the key to the next largest |
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121 | * int key. Weird behavior I can't understand. For example $cache["123"] will become $cache[0] |
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122 | * |
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123 | * @param str $key An identifier for the cached object. |
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124 | * @param mixed $var The var to store in the session cache. |
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125 | * @param bool $flags If we have something really big that we |
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126 | * still want to cache, setting this to |
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127 | * CACHE_ALLOW_OVERSIZED allows this. |
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128 | * @return bool True on success, false otherwise. |
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129 | */ |
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130 | function set($key, $var, $flags=0) |
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131 | { |
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132 | $app =& App::getInstance(); |
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133 | |
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134 | if (true !== $this->getParam('enabled')) { |
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135 | $app->logMsg(sprintf('Cache not enabled, not saving data.', null), LOG_DEBUG, __FILE__, __LINE__); |
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136 | return false; |
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137 | } |
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138 | |
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139 | $var = serialize($var); |
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140 | $var_len = strlen($var); |
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141 | |
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142 | if ($var_len >= $this->getParam('item_size_limit')) { |
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143 | $app->logMsg(sprintf('Serialized variable (%s bytes) more than item_size_limit (%s bytes).', $var_len, $this->getParam('item_size_limit')), LOG_NOTICE, __FILE__, __LINE__); |
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144 | return false; |
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145 | } |
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146 | |
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147 | if ($flags & CACHE_ALLOW_OVERSIZED == 0 && $var_len >= $this->getParam('stack_size_limit')) { |
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148 | $app->logMsg(sprintf('Serialized variable (%s bytes) more than stack_size_limit (%s bytes).', $var_len, $this->getParam('stack_size_limit')), LOG_NOTICE, __FILE__, __LINE__); |
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149 | return false; |
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150 | } |
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151 | |
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152 | // Remove any value already stored under this key. |
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153 | unset($_SESSION['_cache'][$this->_ns][$key]); |
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154 | |
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155 | // Continue to prune the cache if its size is greater than stack_size_limit, but keep at least min_items. |
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156 | while (strlen(serialize($_SESSION['_cache'][$this->_ns])) + $var_len >= $this->getParam('stack_size_limit') && sizeof($_SESSION['_cache'][$this->_ns]) >= $this->getParam('min_items')) { |
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157 | array_shift($_SESSION['_cache'][$this->_ns]); |
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158 | } |
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159 | |
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160 | // Save this value under the specified key. |
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161 | $_SESSION['_cache'][$this->_ns][$key] =& $var; |
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162 | |
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163 | if ($var_len >= 1024000) { |
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164 | $app->logMsg(sprintf('Successfully cached oversized variable (%s bytes).', $var_len), LOG_DEBUG, __FILE__, __LINE__); |
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165 | } |
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166 | |
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167 | return true; |
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168 | } |
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169 | |
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170 | /** |
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171 | * Retrives an object from the session cache and returns it unserialized. |
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172 | * It also moves it to the top of the stack, which makes it such that the |
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173 | * cache flushing mechanism of putCache deletes the oldest referenced items |
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174 | * first. |
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175 | * |
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176 | * @param string $key The key for the datum to retrieve. |
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177 | * @return mixed The requested datum, or false on failure. |
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178 | */ |
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179 | function get($key) |
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180 | { |
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181 | $app =& App::getInstance(); |
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182 | |
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183 | if (true !== $this->getParam('enabled')) { |
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184 | $app->logMsg(sprintf('Cache not enabled, not getting data.', null), LOG_DEBUG, __FILE__, __LINE__); |
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185 | return false; |
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186 | } |
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187 | |
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188 | if (array_key_exists($key, $_SESSION['_cache'][$this->_ns])) { |
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189 | $app->logMsg(sprintf('Retreiving %s from cache.', $key), LOG_DEBUG, __FILE__, __LINE__); |
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190 | // Move the accessed cached datum to the top of the stack. Maybe somebody knows a better way to do this? |
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191 | $tmp =& $_SESSION['_cache'][$this->_ns][$key]; |
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192 | unset($_SESSION['_cache'][$this->_ns][$key]); |
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193 | $_SESSION['_cache'][$this->_ns][$key] =& $tmp; |
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194 | // Return the unserialized datum. |
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195 | return unserialize($_SESSION['_cache'][$this->_ns][$key]); |
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196 | } else { |
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197 | $app->logMsg(sprintf('Missing %s from cache.', $key), LOG_DEBUG, __FILE__, __LINE__); |
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198 | return false; |
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199 | } |
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200 | } |
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201 | |
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202 | /** |
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203 | * Tells you if the object is cached. |
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204 | * |
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205 | * @param string $key The key of the object to check. |
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206 | * @return bool True if a value exists for the given key. |
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207 | */ |
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208 | function exists($key) |
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209 | { |
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210 | if (true !== $this->getParam('enabled')) { |
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211 | return false; |
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212 | } |
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213 | |
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214 | return array_key_exists($key, $_SESSION['_cache'][$this->_ns]); |
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215 | } |
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216 | |
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217 | /** |
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218 | * Removes a cached object. |
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219 | * |
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220 | * @param string $key The key of the object to check. |
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221 | * @return bool True if the value existed before being unset. |
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222 | */ |
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223 | function delete($key) |
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224 | { |
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225 | if (array_key_exists($key, $_SESSION['_cache'][$this->_ns])) { |
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226 | unset($_SESSION['_cache'][$this->_ns][$key]); |
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227 | return true; |
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228 | } else { |
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229 | return false; |
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230 | } |
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231 | } |
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232 | |
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233 | /* |
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234 | * Delete all existing items from the cache. |
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235 | * |
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236 | * @access public |
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237 | * @author Quinn Comendant <quinn@strangecode.com> |
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238 | * @version 1.0 |
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239 | * @since 05 Jun 2006 23:51:34 |
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240 | */ |
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241 | function clear() |
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242 | { |
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243 | $_SESSION['_cache'][$this->_ns] = array(); |
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244 | } |
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245 | |
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246 | // END Cache |
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247 | } |
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248 | |
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249 | ?> |
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