我正在尝试在我的数据库字段上做Memoizaiton，我想我犯了一个错误，因为它不打印$fieldCache数组的结果。
我对PHP中的OOP很新，所以如果有人可以提供帮助并给我一些建议，我会很高兴。
这是我的班级代码：
<?php
class Main{
public $id;
public $maxT;
public $meanT;
public $minT;
public $dewP;
public $meanDP;
public $minDP;
public $maxH;
public $meanH;
public $minH;
public $maxSLP;
public $meanSLP;
public $minSLP;
public $maxV;
public $meanV;
public $minV;
public $maxWS;
public $meanWS;
public $maxGS;
public $prec;
public $cloudCover;
public $event;
public $windDir;
public static $fieldCache=array();
public function getID($table,$date){
return $this->_data('id',$table,$date);
}
public function getMaxT($table,$date){
return $this->_data('MaxTemperatureC',$table,$date);
}
public function getMeanT($table,$date){
return $this->_data('MeanTemperatureC',$table,$date);
}
public function getMinT($table,$date){
return $this->_data('MinTemperatureC',$table,$date);
}
public function getDewP($table,$date){
return $this->_data('DewPointC',$table,$date);
}
public function getMeanDewP($table,$date){
return $this->_data('MeanDewPointC',$table,$date);
}
public function getMinDewP($table,$date){
return $this->_data('MinDewPointC',$table,$date);
}
public function getMaxH($table,$date){
return $this->_data('MaxHumidity',$table,$date);
}
public function getMeanH($table,$date){
return $this->_data('MeanHumidity',$table,$date);
}
public function getMinH($table,$date){
return $this->_data('MinHumidity',$table,$date);
}
public function getMaxSLP($table,$date){
return $this->_data('MaxSeaLevelPressurehPa',$table,$date);
}
public function getMeanSLP($table,$date){
return $this->_data('MeanSeaLevelPressurehPa',$table,$date);
}
public function getMinSLP($table,$date){
return $this->_data('MinSeaLevelPressurehPa',$table,$date);
}
public function getMaxV($table,$date){
return $this->_data('MaxVisibilityKm',$table,$date);
}
public function getMeanV($table,$date){
return $this->_data('MeanVisibilityKm',$table,$date);
}
public function getMinV($table,$date){
return $this->_data('MinVisibilityKm',$table,$date);
}
public function getMaxWS($table,$date){
return $this->_data('MaxWindSpeedKmh',$table,$date);
}
public function getMeanWS($table,$date){
return $this->_data('MeanWindSpeedKmh',$table,$date);
}
public function getMaxGS($table,$date){
return $this->_data('MaxGustSpeedKmh',$table,$date);
}
public function getPrec($table,$date){
return $this->_data('Precipitationmm',$table,$date);
}
public function getCloudCover($table,$date){
return $this->_data('CloudCover',$table,$date);
}
public function getEvent($table,$date){
return $this->_data('Events',$table,$date);
}
public function getWindDir($table,$date){
return $this->_data('WindDirDegrees',$table,$date);
}
private function _data($field,$table,$date){
global $fieldCache;
//echo ' field : '.$field." | table: ".$table." | date: ".$date."<br />";
$dbh=new PDO("sqlite2:sqlite/dbTest1.db",null,null,array(PDO::ATTR_PERSISTENT=>true)) or die("<link rel='stylesheet' type='text/css' href='../css/style.css' title='Default' />
<center><h3><span class='blue'>Oh my!</span><span class='yellow'> Our</span><span class='red'> database</span><span class='green'> is</span>
<span class='blue'>trying</span><span class='yellow'> to escape!</span> <span class='red'>We</span><span class='green'> have dispatched</span><span class='blue'> a team of highly koal-ified</span>
<span class='green'>koalas</span><span class='yellow'> to</span><span class='red'> catch it!</span> <span class='blue'>Please</span><span class='red'> try again</span><span class='green'> later</span><span class='yellow'>!</span>
<br />
<img src='images/koala_running.gif'><center/><h3 />");
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
//MemoizationCheck for stored results
if(isset(self::$fieldCache[$field][$table][$date])){
echo self::$fieldCache[$field][$table][$date];
return self::$fieldCache[$field][$table][$date];
}
$query=$dbh->query("SELECT $field FROM $table WHERE Date=$date");
$result=$query->fetch(PDO::FETCH_ASSOC);
self::$fieldCache[$field][$table][$date]=$result;
echo self::$fieldCache[$table][$date];
return $result[$field];
echo $result[$field];
unset($dbh);
}
}
?>
从我的其他文件设置：
$obj=new Main();
$id=$obj->getID($Country,$datepicker);
$maxT=$obj->getMaxT($Country,$datepicker);
$meanT=$obj->getMeanT($Country,$datepicker);
$minT=$obj->getMinT($Country,$datepicker);
$dewP=$obj->getDewP($Country,$datepicker);
$meanDP=$obj->getMeanDewP($Country,$datepicker);
$minDP=$obj->getMinDewP($Country,$datepicker);
$maxH=$obj->getMaxH($Country,$datepicker);
$meanH=$obj->getMeanH($Country,$datepicker);
$minH=$obj->getMinH($Country,$datepicker);
$maxSLP=$obj->getMaxSLP($Country,$datepicker);
$meanSLP=$obj->getMeanSLP($Country,$datepicker);
$minSLP=$obj->getMinSLP($Country,$datepicker);
$maxV=$obj->getMaxV($Country,$datepicker);
$meanV=$obj->getMeanV($Country,$datepicker);
$minV=$obj->getMinV($Country,$datepicker);
$maxWS=$obj->getMaxWS($Country,$datepicker);
$meanWS=$obj->getMeanWS($Country,$datepicker);
$maxGS=$obj->getMaxGS($Country,$datepicker);
$prec=$obj->getPrec($Country,$datepicker);
$cloudCover=$obj->getCloudCover($Country,$datepicker);
$event=$obj->getEvent($Country,$datepicker);
$windDir=$obj->getWindDir($Country,$datepicker);
答案 0 :(得分：0)
您可以通过在PHP之前应用$fieldCache关键字来访问静态属性（例如self）
if(isset(self::$fieldCache[$field][$table][$date])){
return self::$fieldCache[$field][$table][$date];
}
self指的是当前的课程
并且无需global财产