我在这里有点时间，我正在尝试在自己（;）之后正确清理，并显示我的班级和方法正在使用多少内存。
我遇到的问题是：
这是课程，测试页面和结果（以及在线结果）
CLASS：
<?php
class o7thDB {
public $Type = 1; // What type of database are we connecting to
public $Host = ''; // The host server we are connecting to
public $Name = ''; // The name of the database
public $User = ''; // The user to login with
public $Pass = ''; // The password to login with
public $Query = ''; // The query to execute
public $Params = array(); // An array of parameters to pass to the query for execution
public $ShouldCache = false; // Should the results be cached?
public $CacheKey = ''; // What should we name the key for this cache?
public $Exceptions = ''; // Returns a string representing the exception that occurred if any
/* Memory Usage Tests */
public $InitialMemory;
public $PreSelectMemory;
public $CreatePDOMemory;
public $PostSelectMemory;
public $PreReturnMemory;
protected $DBHandle;
protected $Cache;
protected function Connect(){
$this->InitialMemory = memory_get_peak_usage();
if(session_status() != PHP_SESSION_ACTIVE){
session_start();
}
$dsn = array();
switch ($this->Type) {
case 1: // MS SQL
$dsn = array("mssql:host=$this->Host;dbname=$this->Name", $this->User, $this->Pass);
break;
case 2: // MS SQL Server
$dsn = array("sqlsrv:server=$this->Host;database=$this->Name", $this->User, $this->Pass);
break;
case 3: // MS Access
$dsn = array("odbc:Driver={Microsoft Access Driver (*.mdb)};Dbq=$this->Name;Uid=$this->User");
break;
case 4: // Oracle
$dsn = array("OCI:dbname=$this->Name;charset=UTF-8", $this->User, $this->Pass);
break;
case 5: // Informix
$dsn = array("informix:DSN=$this->Name", $this->User, $this->Pass);
break;
case 6: // Firebird
$dsn = array("firebird:dbname=$this->Host:$this->Name", $this->User, $this->Pass);
break;
case 7: // MySQL
$dsn = array("mysql:host=$this->Host;dbname=$this->Name", $this->User, $this->Pass);
break;
case 8: // SQLLite
$dsn = array("sqlite:$this->Host");
break;
default: // MySQL
$dsn = array("mysql:host=$this->Host;dbname=$this->Name", $this->User, $this->Pass);
break;
}
try{
$this->DBHandle = new PDO($dsn[0], $dsn[1], $dsn[2]);
$this->DBHandle->setAttribute(PDO::ATTR_PERSISTENT, true);
$this->DBHandle->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$this->CreatePDOMemory = memory_get_peak_usage();
} catch (PDOException $e) {
$this->Exceptions = $e->getMessage();
}
}
// Destroying Everything
public function __destruct(){
unset($this->DBHandle, $this->Cache, $this->Type, $this->Host, $this->Name, $this->User, $this->Pass,
$this->Query, $this->Params, $this->ShouldCache, $this->CacheKey, $this->Exceptions);
}
// Executes a query against the database, returns boolean success
public function Execute(){
}
// Executes a select statement against the database, returns an associative array
public function Select(){
$this->Connect();
$this->PreSelectMemory = memory_get_peak_usage();
$stmt = $this->DBHandle->prepare($this->Query);
$stmt->execute($this->Params);
$ret = $stmt->fetchAll(PDO::FETCH_ASSOC);
$this->PostSelectMemory = memory_get_peak_usage();
if($this->ShouldCache){
$cKey = $this->CacheKey . session_id();
if(isset($this->Cache[$cKey])){
$this->PreReturnMemory = memory_get_peak_usage();
return $this->Cache[$cKey];
}else{
$this->PreReturnMemory = memory_get_peak_usage();
$this->Cache[$cKey] = $ret;
return $ret;
}
}else{
$this->PreReturnMemory = memory_get_peak_usage();
return $ret;
}
$stmt->closeCursor();
unset($stmt, $ret);
}
}
?>
测试页：
<?php
// Show All Errors
error_reporting(E_ALL);
ini_set('display_errors', '1');
require_once($_SERVER['DOCUMENT_ROOT'] . '/Database/o7th.db.class.php');
// Time the Execution
$mtime = microtime();
$mtime = explode(" ",$mtime);
$mtime = $mtime[1] + $mtime[0];
$starttime = $mtime;
$db = new o7thDB();
$db->Type = 7;
$db->Host = 'localhost';
$db->Name = 'mydb';
$db->User = 'myun';
$db->Pass = 'mypw';
$db->Query = "Select * From `modx_session` Where `data` Like ? Or `id` Like ?";
$db->ShouldCache = true;
$db->CacheKey = 'a';
$db->Params = array('%a%', '%Welcome%');
$ret = $db->Select();
$rCt = count($ret);
echo $rCt . ': Records Returned<br />';
echo $db->Exceptions;
unset($ret);
echo $db->InitialMemory . ': Initial Memory<br />';
echo $db->CreatePDOMemory . ': Create PDO Memory<br />';
echo $db->PreSelectMemory . ': Pre-Select Memory<br />';
echo $db->PostSelectMemory . ': Post-Select Memory<br />';
echo $db->PreReturnMemory . ': Pre-Return Memory<br />';
unset($db);
echo memory_get_peak_usage() .': After all is said and done!<br />';
echo '<hr />';
$mtime = microtime();
$mtime = explode(" ",$mtime);
$mtime = $mtime[1] + $mtime[0];
$endtime = $mtime;
$totaltime = ($endtime - $starttime);
echo "This page was created in ".$totaltime." seconds";
?>
测试页面结果：
21168: Records Returned
288016: Initial Memory
288016: Create PDO Memory
288016: Pre-Select Memory
19209456: Post-Select Memory
19209552: Pre-Return Memory
19209768: After all is said and done!
This page was created in 0.066221952438354 seconds
所以，我的问题是，为什么代码会占用更多内存，毕竟清理完毕后呢？
答案 0 :(得分：-1)
PHP进程不释放已释放的内存。通过释放PHP脚本中的内存，您只需使其可供同一进程使用。但是整个进程总是拥有它在运行时分配的所有内存。
这就是为什么在PHP中不需要自己进行清理 - 无论如何你无法在脚本运行时将它返回到系统，但整个运行时只需要几分之一 - 所以，没有必要打扰。
顺便说一下，你的班级看起来太错了......想象一下 坦率地说，它旨在解决想象中的问题，而不是真正的问题。就像连接到所有可能的数据库一样。同时它缺乏非常重要的东西。
基于会话的缓存机制看起来很糟糕。它确实会用很多的无用数据污染你的记忆。
所有这些重复的“缓存”消耗了你太在意的记忆。
因此，效果将是相反的 - 而不是加速您的网站，这个缓存实际上会使它变得缓慢和臃肿。
这就是为什么说： “过早优化是所有邪恶的根源”