memory_get_usage()這個方法是返回當前分配給PHP腳本的內存量，首先先把查詢初始分配給的內存量存儲到變量$m1,然后聲明$var_string變量并賦值。這時因為聲明了$var_string變量所以內存量就變大了，所以這時再用當前的內存量減掉之前$m1的內存量就可以計算出$var_string所占的內存量。下面的也是同理。

<?php?

echo $m1 = memory_get_usage();?

echo "<br />";

$var_string = "123";

echo $m2 = memory_get_usage()-$m1;?

echo "<br />";

$n = "123";

echo $m3 = memory_get_usage()-$m1-$m2;?

echo "<br />";

$float = "123.00";

echo $m4 = memory_get_usage()-$m1-$m2-$m3;?

echo "<br />";

$var_array = array("123");

echo $m5 = memory_get_usage()-$m1-$m2-$m3-$m4;?

?>