正規表現のサブパターンの詳細説明、正規表現の詳細説明_PHPチュートリアル

<?<span>php
    </span><span>$time</span> = <span>date</span> ("Y-m-d H:i:s"<span>);
    </span><span>$pattern</span> = "/\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}/i"<span>; 
    </span><span>if</span>(<span>preg_match</span>(<span>$pattern</span>,<span>$time</span>,<span>$arr</span><span>)){
    </span><span>echo</span> "<pre class="brush:php;toolbar:false">"<span>;
    </span><span>print_r</span>(<span>$arr</span><span>);        
    </span><span>echo</span> "

<span>Array
(
    [0] => 2012-06-23 03:08:45
)</span>

<?<span>php
    </span><span>$time</span> = <span>date</span> ("Y-m-d H:i:s"<span>);
    </span><span>$pattern</span> = "/<span>(</span>\d{4}<span><strong>)</strong></span>-<span>(</span>\d{2}<span>)</span>-<span>(</span>\d{2}<span>)</span> <span>(</span>\d{2}<span>)</span>:<span>(</span>\d{2}<span>)</span>:<span>(</span>\d{2}<span>)</span>/i"<span>; 
    </span><span>if</span>(<span>preg_match</span>(<span>$pattern</span>,<span>$time</span>,<span>$arr</span><span>)){
    </span><span>echo</span> "<pre class="brush:php;toolbar:false">"<span>;
    </span><span>print_r</span>(<span>$arr</span><span>);        
    </span><span>echo</span> "

<span>Array</span><span>
(
    [</span>0] => 2012-06-23 03:19:23<span>
    [</span>1] => 2012<span>
    [</span>2] => 06<span>
    [</span>3] => 23<span>
    [</span>4] => 03<span>
    [</span>5] => 19<span>
    [</span>6] => 23<span>
)</span>

总结：我们可以使用小括号给整个匹配模式进行分组，默认情况下，每个分组会自动拥有一个组号，规则是，从左到右，以分组的左括号为标志，第一个出现的分组为组号1，第二个为组号2，以此类推。其中，分组0对应整个正则表达式。<br />对整个正则匹配模式进行了分组以后，就可以进一步使用&ldquo;向后引用&rdquo;来重复搜索前面的某个分组匹配的文本。例如：\1代表分组1匹配的文本，\2代表分组2匹配的文本等等<br />我们可以进一步修改下代码，如下所示：

<?<span>php
    </span><span>$time</span> = <span>date</span> ("Y-m-d H:i:s"<span>);
    </span><span>$pattern</span> = "/(\d{4})-(\d{2})-(\d{2}) (\d{2}):(\d{2}):(\d{2})/i"<span>;
    </span><span>$replacement</span> = "\$time格式为：$0<BR>替换后的格式为：\\1年\\2月\\3日 \\4时\\5分\\6秒"<span>;
    </span><span>print</span> <span>preg_replace</span>(<span>$pattern</span>, <span>$replacement</span>, <span>$time</span><span>);
    </span><span>if</span>(<span>preg_match</span>(<span>$pattern</span>,<span>$time</span>,<span>$arr</span><span>)){
        </span><span>echo</span> "<pre class="brush:php;toolbar:false">"<span>;
        </span><span>print_r</span>(<span>$arr</span><span>);        
        </span><span>echo</span> "

<span>$time格式为</span>：2012-06-23 03:30:31<span>
替换后的格式为：2012年06月23日 03时30分31秒
</span><span>Array</span><span>
(
    [</span>0] => 2012-06-23 03:30:31<span>
    [</span>1] => 2012<span>
    [</span>2] => 06<span>
    [</span>3] => 23<span>
    [</span>4] => 03<span>
    [</span>5] => 30<span>
    [</span>6] => 31<span>
)</span>

<br /><br />