谁能告诉我这个问题怎么写
<?php
echo $m1 = memory_get_usage();
echo "<br />";
echo $m2 = memory_get_usage()-$m1;
echo "<br />";
echo $m3 = memory_get_usage()-$m1-$m2;
echo "<br />";
echo $m4 = memory_get_usage()-$m1-$m2-$m3;
echo "<br />";
echo $m5 = memory_get_usage()-$m1-$m2-$m3-$m4;
?>
怎么写