php preg_match_all 匹配错误的字符串

Question

我有这个子模式:

<?php                                                                                                                                                                                                                                          

    $wavs = 'aaaa="" wav="d" bbbbb="" wav="gerg" ccccc="" wav="" ddddd=""';        
    preg_match_all('#(?<=wav=").+?(?=")#', $wavs, $matches);                    
    print_r($matches);                                                          
?> 

它的结果是这样的输出:

php test.php 
Array
(
    [0] => Array
        (
            [0] => d
            [1] => gerg
            [2] => " ddddd=
        )

)

虽然我预计只有 2 场比赛:

php test.php 
Array
(
    [0] => Array
        (
            [0] => d
            [1] => gerg
        )

)

这里有什么问题？为什么会捕获额外的无关字符串？

编辑:(M42 响应)

preg_match_all('#(?<=wav=").*?(?=")#', $wavs, $matches);  

仍然会导致不正确的匹配:

Array
(
    [0] => Array
        (
            [0] => d
            [1] => gerg
            [2] => 
            [3] => " ddddd=
        )

)

编辑:(嗅探器)

我的天哪!谢谢你，先生!完全有效!

preg_match_all('#(?<=wav=")\w+?(?=")#', $wavs, $matches);  

Array
(
    [0] => Array
        (
            [0] => d
            [1] => gerg
        )

)

Answer 1

这里有什么问题？为什么会捕获额外的无关字符串？

 #(?<=wav=").+?(?=")#
            ^^^
         This is the reason, it matches everything including the space and the "

你可能想要:

#(?<wav=")\w+(?=")#