在PHP中正则表达式用于复杂字符串的处理。所支持的正则表达式如下: ereg() ereg_replace() eregi() eregi_replace() split() (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。 Example 2-4. Regular expression examples ereg("abc",$string); /* Returns true if "abc" is found anywhere in $string. */ ereg("^abc",$string); /* Returns true if "abc" is found at the beginning of $string. */ ereg("abc$",$string); /* Returns true if "abc" is found at the end of $string. */ eregi("(ozilla.[23]|MSIE.3)",$HTTP_USER_AGENT); /* Returns true if client browser is Netscape 2, 3 or MSIE 3. */ ereg("([[:alnum:]]+) ([[:alnum:]]+) ([[:alnum:]]+)",$string,$regs); /* Places three space separated words into $regs[1], $regs[2] and $regs[3]. */ ereg_replace("^"," ",$string); /* Put a tag at the beginning of $string. */ ereg_replace("$"," ",$string); /* Put a tag at the end of $string. */ ereg_replace("\n","",$string); /* Get rid of any carriage return characters in $string. */ |
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