Interpret the specific code implementation of PHP to calculate page execution time_PHP tutorial

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<span><strong><font color="#006699"><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> </SPAN></SPAN><LI class=""><SPAN>class runtime  </SPAN><LI class=alt><SPAN>{  </SPAN><LI class=""><SPAN>    var $</SPAN><SPAN class=attribute><FONT color=#ff0000>StartTime</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>0</FONT></SPAN><SPAN>;  </SPAN></SPAN><LI class=alt><SPAN>    var $</SPAN><SPAN class=attribute><FONT color=#ff0000>StopTime</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>0</FONT></SPAN><SPAN>;  </SPAN></SPAN><LI class=""><SPAN>   </SPAN><LI class=alt><SPAN>    function get_microtime()  </SPAN><LI class=""><SPAN>    {  </SPAN><LI class=alt><SPAN>        list($usec, $sec) = explode(' ', microtime());  </SPAN><LI class=""><SPAN>        return ((float)$usec + (float)$sec);  </SPAN><LI class=alt><SPAN>    }  </SPAN><LI class=""><SPAN>   </SPAN><LI class=alt><SPAN>    function start()  </SPAN><LI class=""><SPAN>    {  </SPAN><LI class=alt><SPAN>        $this-</SPAN><SPAN class=tag><STRONG><FONT color=#006699>></span></font></strong></span><span class="attribute"><font color="#ff0000">StartTime</font></span><span> = $this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>get_microtime();  </span>
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<li class=""><span>    }  </span></li>
<li class="alt"><span>   </span></li>
<li class=""><span>    function stop()  </span></li>
<li class="alt"><span>    {  </span></li>
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<span>        $this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span class="attribute"><font color="#ff0000">StopTime</font></span><span> = $this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>get_microtime();  </span>
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<li class="alt"><span>    }  </span></li>
<li class=""><span>   </span></li>
<li class="alt"><span>    function spent()  </span></li>
<li class=""><span>    {  </span></li>
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<span>        return round(($this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>StopTime - $this-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>StartTime) * 1000, 1);  </span>
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<li class=""><span>    }  </span></li>
<li class="alt"><span>   </span></li>
<li class=""><span>}  </span></li>
<li class="alt"><span>   </span></li>
<li class=""><span>   </span></li>
<li class="alt"><span>//例子  </span></li>
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<span>$</span><span class="attribute"><font color="#ff0000">runtime</font></span><span>= </span><span class="attribute-value"><font color="#0000ff">new</font></span><span> runtime;  </span>
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<span>$runtime-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>start();  </span>
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<li class=""><span>   </span></li>
<li class="alt"><span>//你的代码开始  </span></li>
<li class=""><span>   </span></li>
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<span>$</span><span class="attribute"><font color="#ff0000">a</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">0</font></span><span>;  </span>
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<span>for($</span><span class="attribute"><font color="#ff0000">i</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">0</font></span><span>; $i</span><strong><font color="#006699"><span class="tag"><</SPAN><SPAN class=tag-name>1000000</SPAN></FONT></STRONG><SPAN>; $i++)  </SPAN></SPAN><LI class=alt><SPAN>{  </SPAN><LI class=""><SPAN>    $a += $i;  </SPAN><LI class=alt><SPAN>}  </SPAN><LI class=""><SPAN>   </SPAN><LI class=alt><SPAN>//你的代码结束  </SPAN><LI class=""><SPAN>   </SPAN><LI class=alt><SPAN>$runtime-</SPAN><SPAN class=tag><STRONG><FONT color=#006699>></span></font></strong><span>stop();  </span>
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<span>echo "页面执行时间: ".$runtime-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>spent()." 毫秒";  </span>
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<li class="alt"><span>   </span></li>
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<span></span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
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