php是我们现在最常用的动态开发web页面的语言，字符串的处理在编程中是最长用到的，我们这里就详细的谈谈php substr的利用。有一堆类似以下变量$abc的字符串，末尾都多出来了一个,(逗号)，我想去掉末尾的逗号，为了验证不同的处理方法的执行时间，以下是我写的一个对比程序进行试验：
程序一，PHP substr
<OL class=dp-xml><LI class=alt><SPAN><STRONG><FONT color=#006699><SPAN class=tag><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> </SPAN></SPAN><LI class=""><SPAN>function getmicrotime(){ </SPAN><LI class=alt><SPAN>list($usec, $sec) = explode(" ",microtime()); </SPAN><LI class=""><SPAN>return ((float)$usec + (float)$sec); </SPAN><LI class=alt><SPAN>} </SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>time_start</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>getmicrotime</FONT></SPAN><SPAN>(); </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>abc</FONT></SPAN><SPAN>=</SPAN><SPAN class=attribute-value><FONT color=#0000ff>"重庆,万州,涪陵,渝中,大渡口,江北,沙坪坝,九龙坡,南岸,北碚,万盛,双挢,渝北,巴南,黔江,长寿,綦江,潼南,铜梁,<br>大足,荣昌,壁山,梁平,城口,丰都,垫江,武隆,忠县,开县,云阳,奉节,巫山,巫溪,石柱,"</FONT></SPAN><SPAN>; </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>l</FONT></SPAN><SPAN>=</SPAN><SPAN class=attribute-value><FONT color=#0000ff>strlen</FONT></SPAN><SPAN>($abc); </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>abc</FONT></SPAN><SPAN>=</SPAN><SPAN class=attribute-value><FONT color=#0000ff>substr</FONT></SPAN><SPAN>($abc,0,$l-1); </SPAN></SPAN><LI class=""><SPAN>echo $abc."</SPAN><STRONG><FONT color=#006699><SPAN class=tag><</SPAN><SPAN class=tag-name>br</SPAN><SPAN class=tag>></SPAN></FONT></STRONG><SPAN>"; </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>time_end</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>getmicrotime</FONT></SPAN><SPAN>(); </SPAN></SPAN><LI class=""><SPAN>echo ($time_end-$time_start)*1000; </SPAN><LI class=alt><SPAN></SPAN><SPAN class=tag><STRONG><FONT color=#006699>?></FONT></STRONG></SPAN><SPAN> </SPAN></SPAN></LI></OL>程序二，利用正则表达式
<OL class=dp-xml><LI class=alt><SPAN><SPAN class=tag><?</SPAN><SPAN class=tag-name>php</SPAN><SPAN> </SPAN></SPAN><LI class=""><SPAN>function getmicrotime(){ </SPAN><LI class=alt><SPAN>list($usec, $sec) = explode(" ",microtime()); </SPAN><LI class=""><SPAN>return ((float)$usec + (float)$sec); </SPAN><LI class=alt><SPAN>} </SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>time_start</SPAN><SPAN> = </SPAN><SPAN class=attribute-value>getmicrotime</SPAN><SPAN>(); </SPAN></SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>abc</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"重庆,万州,涪陵,渝中,大渡口,江北,沙坪坝,九龙坡,南岸,北碚,万盛,双挢,渝北,巴南,黔江,长寿,綦江,潼南,铜梁,<br>大足,荣昌,壁山,梁平,城口,丰都,垫江,武隆,忠县,开县,云阳,奉节,巫山,巫溪,石柱,"</SPAN><SPAN>; </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>abc</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>str_replace</SPAN><SPAN>(",$","",$abc); </SPAN></SPAN><LI class=alt><SPAN>echo $abc."</SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>br</SPAN><SPAN class=tag>></SPAN><SPAN>"; </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>time_end</SPAN><SPAN> = </SPAN><SPAN class=attribute-value>getmicrotime</SPAN><SPAN>(); </SPAN></SPAN><LI class=alt><SPAN>echo ($time_end-$time_start)*1000; </SPAN><LI class=""><SPAN></SPAN><SPAN class=tag>?></SPAN><SPAN> </SPAN></SPAN></LI></OL>
