为什么我PHP函数执行问没有释放内存

function importTestSuiteFormArray1($db,$parentID,$tproject_id,$userID,$duplicateLogic,&$testsuiteArray,&$testcaseArray){	global $productIndex;	$unexistPF = array();//用于存放当前项目中没有的excel文件存在的平台	$produceRelFB = array();	$resultMap = null;	$tsResult = null;//测试套件导入结果	$tables = tlObject::getDBTables("platforms");	$pfSql = " select id,name from ".$tables['platforms']." where testproject_id=$tproject_id";	$pfRe = $db->fetchColumnsIntoMap($pfSql,"id","name");	$pfRe = is_null($pfRe) ? array() : $pfRe;	foreach($productIndex as $vKey=>$pItem){		if(!in_array($vKey, $pfRe)){			$unexistPF[] = $vKey;		}	}//	$memory1 = memory_get_usage();//	$fileName = date("md-His");//	$hand = fopen("e:/testcase/".$fileName.".txt","a+");//	$bTime = microtime_float();	$tempTSArray = array();	$createSuc = "创建成功。";	$updateSuc = "更新成功。";	if(is_array($testsuiteArray) && count($testsuiteArray)>0){		foreach($testsuiteArray as $key=>$tsItem){//			$begin = microtime_float();			if ($tsItem['name'] != "")			{				if($tsItem['parentNum']==0){					$parID = $parentID;				}else{					$parID = $tempTSArray[$key]['parentID'];				}				$tsuiteMgr = new testsuite($db);				$info = $tsuiteMgr->get_by_name($tsItem['name'],$parID);				if( is_null($info) )				{					$ret = $tsuiteMgr->create($parID,$tsItem['name'],"",$tsItem['node_order']);					$tsuiteID = $ret['id'];					$tsResult[] = array($tsItem['name'],$createSuc);									}				else				{					$tsuiteID = $info[0]['id'];					$ret = $tsuiteMgr->update($tsuiteID,$tsItem['name'],"",null,$tsItem['node_order']);					$tsResult[] = array($tsItem['name'],$updateSuc);				}				if(is_array($tsItem['children']) && count($tsItem['children'])>0){					foreach($tsItem['children'] as $val){						$tempTSArray[$val]['parentID'] = $tsuiteID;					}				}								}//			$end = microtime_float();//			fwrite($hand, "每条规约用时：".($end-$begin)."\r\n");			}	}//	echo "testsuiteArray前".memory_get_usage()."<br>";	$testsuiteArray = null;//	echo "testsuiteArray后".memory_get_usage()."<br>";	$GLOBALS['testsuiteArray']=null;//	echo "全局testsuiteArray后".memory_get_usage()."<br>";	if(is_array($testcaseArray) && count($testcaseArray)>0){		$tcData = array();//		$begin = microtime_float();		$flag = 0;		foreach ($testcaseArray as $key=>$tsItem){			if($tsItem['parentNum']==0){				$parID = $parentID;			}else{				$parID = $tempTSArray[$key]['parentID'];			}			$tcData[$flag] = array(								"name"=>$tsItem['name'],								"node_order"=>$tsItem['order'],								"parentID"=>$parID			) ;			if(is_array($tsItem['property']) && count($tsItem['property'])>0){				foreach($tsItem['property'] as $pKey=>$val){					$tcData[$flag][$pKey] = $val;				}			}			if(is_array($tsItem['custom_fields']) && count($tsItem['custom_fields'])>0){				foreach($tsItem['custom_fields'] as $cfName=>$cfValue){					$tcData[$flag][customfields][] = array("name"=>$cfName,"value"=>$cfValue);				}			}			if(is_array($tsItem['srs']) && count($tsItem['srs'])>0){				$tcData[$flag]['srs'] = $tsItem['srs'];			}			if(is_array($tsItem['produce']) && count($tsItem['produce'])>0){				$tcData[$flag]['produce'] = $tsItem['produce'];			}			$flag++;		}//		$end = microtime_float();//		fwrite($hand, "循环用例时间：".($end-$begin)."\r\n");//		echo "testcaseArray前".memory_get_usage()."<br>";		$testcaseArray = null;//		echo "testcaseArray后".memory_get_usage()."<br>";		$GLOBALS['testcaseArray']=null;//		echo "全局testcaseArray后".memory_get_usage()."<br>";		$tempTSArray = null;//		echo "tempTSArray后".memory_get_usage()."<br>";		if(is_array($tcData) && count($tcData)>0){//			$begin = microtime_float();			$resultMap = saveImportedTCData1($db,$tcData,$tproject_id,$userID,null,$duplicateLogic,$produceRelFB,$pfRe);			$tcData = null;//			echo "tcData后".memory_get_usage()."<br>";//			$memory2 = memory_get_usage();//			$end = microtime_float();//			fwrite($hand, "保存用例总时间：".($end-$begin)."\r\n");//			fwrite($hand, "总用时：".($end-$bTime)."\r\n");//			fwrite($hand, "内存消耗：".($memory2-$memory1)."\r\n");		}	}										$return = array("resultMap"=>$resultMap,"tsResult"=>$tsResult,"unexistPF"=>$unexistPF,"produceRel"=>$produceRelFB);	return $return;//	return $resultMap;	}

$resultMap=saveImportedTCData1($db,$tcData,$tproject_id,$userID,null,$duplicateLogic,$produceRelFB,$pfRe);

  $tcData[$flag][customfields][] = array("name"=>$cfName,"value"=>$cfValue);