PHP正则表达式函数都有那些呢？那么PHP正则表达式函数具体的是代表什么呢？具体的用法又是什么呢？让我们一一向你介绍。PHP正则表达式主要用于复杂字符串的处理。其主要的PHP正则表达式函数如下：
◆ereg()
◆ereg_replace()
◆eregi()
◆eregi_replace()
◆split()
PHP正则表达式函数用法归纳：
(1)ereg,eregi
这是正规表达式匹配函数,前者是大小写有关匹配,后者则是无关的.
用法:
ereg(正规表达式,字符串,[匹配部分数组名]); PHP3.0中的正规表达式大体类似于grep中用的.
(2)ereg_replace,eregi_replace
这些是替换函数.
用法:
ereg_replace(正规表达式,替换串,原字符串);
字符串处理函数中有一个strtr,是"翻译"函数,类似于Perl中的tr/.../.../,
用法:
strtr(字符串,"从","到");
例如:
strtr("aaabb","ab","cd")返回"cccdd".
(3)split
与explode函数有些类似,但这次可以在匹配某正规表达式的地方分割字符串.
用法:
split(正规表达式,字符串,[取出前多少项]);
这些函数都使用正则字符串做为第一个参数。PHP使用Posix 1003.2标准所定义的扩展正则字符串。要查考Posix正则表达式的完整描述请看PHP软件包中regex目录下的man页。
PHP正则表达式函数应用实例：
<ol class="dp-c">
<li class="alt"><span><span class="func">ereg</span><span>(</span><span class="string">"abc"</span><span>,</span><span class="vars">$string</span><span>); </span></span></li>
<li>
<span class="comment">/* Returns true if "abc" is </span> </li>
<li class="alt"><span><span class="comment">found anywhere in $string. */</span><span> </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="func">ereg</span><span>(</span><span class="string">"^abc"</span><span>,</span><span class="vars">$string</span><span>); </span>
</li>
<li>
<span class="comment">/* Returns true if "abc" is </span> </li>
<li class="alt"><span><span class="comment">found at the beginning of $string. */</span><span> </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="func">ereg</span><span>(</span><span class="string">"abc$"</span><span>,</span><span class="vars">$string</span><span>); </span>
</li>
<li>
<span class="comment">/* Returns true if "abc" is </span> </li>
<li class="alt"><span><span class="comment"> found at the end of $string. */</span><span> </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="func">eregi</span><span>(</span><span class="string">"(ozilla.[23]|MSIE.3)"</span><span>,</span><span class="vars">$HTTP_USER_AGENT</span><span>); </span>
</li>
<li>
<span class="comment">/* Returns true if client browser </span> </li>
<li class="alt"><span><span class="comment"> is Netscape 2, 3 or MSIE 3. */</span><span> </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="func">ereg</span><span>("([[:alnum:]]+) ([[:alnum:]]+) </span>
</li>
<li>
<span> ([[:alnum:]]+)",</span><span class="vars">$string</span><span>,</span><span class="vars">$regs</span><span>); </span>
</li>
<li class="alt">
<span class="comment">/* Places three space separated words </span> </li>
<li><span><span class="comment">into $regs[1], $regs[2] and $regs[3]. */</span><span> </span></span></li>
<li class="alt"><span> </span></li>
<li>
<span class="func">ereg_replace</span><span>(</span><span class="string">"^"</span><span>,</span><span class="string">""</span><span>,</span><span class="vars">$string</span><span>); </span>
</li>
<li class="alt">
<span class="comment">/* Put a tag at the beginning of $string. */</span><span> </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="func">ereg_replace</span><span>(</span><span class="string">"$"</span><span>,</span><span class="string">""</span><span>,</span><span class="vars">$string</span><span>); </span>
</li>
<li>
<span class="comment">/* Put a tag at the end of $string. */</span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="func">ereg_replace</span><span>(</span><span class="string">" "</span><span>,</span><span class="string">""</span><span>,</span><span class="vars">$string</span><span>); </span>
</li>
<li class="alt">
<span class="comment">/* Get rid of any carriage </span> </li>
<li><span><span class="comment">return characters in $string. */</span><span> </span></span></li>
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