如何获知PHP程序占用多少内存(memory_get_usage)
下面是使用示例:
复制代码 代码如下:
echo memory_get_usage(), '
'; // 313864
$tmp = str_repeat('http://www.nowamagic.net/', 4000);
echo memory_get_usage(), '
'; // 406048
unset($tmp);
echo memory_get_usage(); // 313952
?>
上面的程序后面的注释代表了它们的输出(单位为 byte(s)),也就是当时 PHP 脚本使用的内存(不含 memory_get_usage() 函数本身占用的内存)。
由上面的例子可以看出,要想减少内存的占用,可以使用 PHP unset() 函数把不再需要使用的变量删除。类似的还有:PHP mysql_free_result() 函数,可以清空不再需要的查询数据库得到的结果集,这样也能得到更多可用内存。
PHP memory_get_usage() 函数还可以有个参数,$real_usage,其值为布尔值。默认为 FALSE,表示得到的内存使用量不包括该函数(PHP 内存管理器)占用的内存;当设置为 TRUE 时,得到的内存为不包括该函数(PHP 内存管理器)占用的内存。
所以在实际编程中,可以用 memory_get_usage() 函数比较各个方法占用内存的高低,来选择使用哪种占用内存小的方法。
贴个使用函数:
复制代码 代码如下:
if (!function_exists('memory_get_usage'))
{
/**
+----------------------------------------------------------
* 取得内存使用情况
+----------------------------------------------------------
* @return integer
+----------------------------------------------------------
*/
function memory_get_usage()
{
$pid = getmypid();
if (IS_WIN)
{
exec('tasklist /FI "PID eq ' . $pid . '" /FO LIST', $output);
return preg_replace('/[^0-9]/', '', $output[5]) * 1024;
}
else
{
exec("ps -eo%mem,rss,pid | grep $pid", $output);
$output = explode(" ", $output[0]);
return $output[1] * 1024;
}
}
}
再来个函数使用例子:
复制代码 代码如下:
//memory_get_usage();
$m1 = memory_get_usage();
echo '
m1:',$m1;//58096
$a = 'hello';
$b = str_repeat($a,1000);
$m2 = memory_get_usage();
echo '
m2:',$m2;//63424
unset($b);
$m3 = memory_get_usage();
echo '
m3:',$m3;//58456
?>

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