熟悉正则的进来下，0宽断言中使用重复*会报错解决办法 -PHP Tutorial-php.cn

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熟悉正则的进来下，0宽断言中使用重复*会报错解决办法

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Jun 13, 2016 pm 01:33 PM

ltword

熟悉正则的进来下，0宽断言中使用重复*会报错
大家看看这两个。

PHP code

<!--

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-->preg_match('#(?).*(?=)#',' pre<a>hi!</a> word',$mt);

------解决方案--------------------
http://perldoc.perl.org/perlretut.html#Looking-ahead-and-looking-behind
这是perl的正则文档，觉得应该可以适用php的正则引擎
里面有一句 The lookahead assertion is denoted by (?=regexp) and the lookbehind assertion is denoted by (?零宽断言也叫环视，上面的意思是逆序环视只能包含固定长度的子表达式，所以不能出现 * ？ +这些量词，只有顺序环视可以

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