惰性匹配(记住:会进行两部操作,请看下面的原理部分)
格式:限定符?
原理:"?":如果前面有限定符,会使用最小的数据。如“*”会取0个,而“+”会取1个,如过是{3,5}会取3个。
先看下面的两个代码:
代码1.
- <?php
- $regex = '/heL*/i';
- $str = 'heLLLLLLLLLLLLLLLL';
- if(preg_match($regex, $str, $matches)){
- var_dump($matches);
- }
- echo "\n";
结果1.
代码2
- <?php
- $regex = '/heL*?/i';
- $str = 'heLLLLLLLLLLLLLLLL';
- if(preg_match($regex, $str, $matches)){
- var_dump($matches);
- }
- echo "\n";
结果2
代码3,使用“+”
- <?php
- $regex = '/heL+?/i';
- $str = 'heLLLLLLLLLLLLLLLL';
- if(preg_match($regex, $str, $matches)){
- var_dump($matches);
- }
- echo "\n";
结果3
代码4,使用{3,5}
- <?php
- $regex = '/heL{3,10}?/i';
- $str = 'heLLLLLLLLLLLLLLLL';
- if(preg_match($regex, $str, $matches)){
- var_dump($matches);
- }
- echo "\n";
结果4
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