我想比较两个函数的执行时间:functionsubject_one(){$str=preg_match_all(...[SNIP]...);//...[SNIP]...return$str;}functionsubject_two(){$reader=newXMLReader;$writer=newXMLWriter;//...[SNIP]...echo$str;}是否可以编写一个函数来执行此操作？例如:functionbenchmark_two_functions($first_function,$second_function){//dostuffreturn$length_of_