用PHP函数memory_get_usage获取当前PHP内存消耗量以实现程序的性能优化
PHP性能优化过程中避免不了需要获取PHP内存消耗,使用memory_get_usage()函数可获取当前的内存消耗情况,函数使用简单,下面以示例的形式介绍下使用 memory_get_usage() 函数获取当前PHP内存消耗量的用法。
一,函数原型int memory_get_usage ([ bool $real_usage=false ] )
二,版本兼容PHP 4 >= 4.3.2,PHP 5
三,基础用法与实例1,获取当前的内存消耗量
<p><?php </p>echo memory_get_usage();<br />$var=str_repeat("www.scutephp.com",10000);<br />echo memory_get_usage();<br />unset($var);<br />echo memory_get_usage();<br /><p>?> </p>
结果输出:62328 122504 62416
说明:memory_get_usage() 函数输出的数值为 bytes 单位2,格式化 memory_get_usage() 结果以 KB 为单位输出
<p><?php </p>function convert($size){ <br /> $unit=array('b','kb','mb','gb','tb','pb');<br /> return @round($size/pow(1024,($i=floor(log($size,1024)))),2).' '.$unit[$i];<br />}<br />echo convert(memory_get_usage(true));<br /><p>?></p>
输出:256 kb3,自定义函数获取数组或变量值大小
<p><?php </p>function array_size($arr){<br /> ob_start();<br /> print_r($arr);<br /> $mem=ob_get_contents();<br /> ob_end_clean();<br /> $mem=preg_replace("/\n +/","",$mem);<br /> $mem=strlen($mem);<br /> return $mem;<br />} <br />$memEstimate=array_size($GLOBALS);<br /><p>?></p>
可以看出,要想减少内存的占用,可以使用 PHP unset() 函数把不再需要使用的变量删除。
类似的还有:
PHP mysql_free_result() 函数,可以清空不再需要的查询数据库得到的结果集,这样也能得到更多可用内存。
PHP memory_get_usage()还可以有个参数,$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PHP memory_get_usage()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。

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