Home Backend Development PHP Tutorial 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

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

Jun 20, 2016 pm 01:02 PM

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>
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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>
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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>
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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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