XML 中的正则表达式使用 PHP：找到某个 xml 标记的某个值

Question

I am trying to get the value of a certain attribute in a certain xml tag with regex but cant get it right, maybe someone has an idea how to do it?

The xml looks like this:

<OTA_PingRQ>
  <Errors>
    <Error Code="101" Type="4" Status="NotProcessed" ShortText="Authentication refused">Authentication : login failed</Error>
  </Errors>
</OTA_PingRQ>

and id like to match only the value of the Shorttext inside the Error tag. in the end it should give me "Authentication refused" back.

What ive tried so far is using a lookbehind and lookahead, which doesnt let me take quantifiers with non fixed width. Like that (?<=<Error.).*?(?=>) . Can someone tell me how to only match the value of the shorttext (inside the error tag)?

Answer 1

You didn't specify the language you're using, i can give you the solution with PHP, the regex remain the same in every language anyway.

Here is the regex you're looking for:

#\<Error Code\=\"[0-9]+\" Type\=\"[0-9]+\" Status\=\"NotProcessed\" ShortText\=\"([a-z 0-9]+)\"\>#is

Concrete PHP use:

$yourOriginalString = '
<OTA_PingRQ>
  <Errors>
    <Error Code="101" Type="4" Status="NotProcessed" ShortText="Authentication refused">Authentication : login failed</Error>
  </Errors>
</OTA_PingRQ>' ;

preg_match_all('#\<Error Code\=\"[0-9]+\" Type\=\"[0-9]+\" Status\=\"NotProcessed\" ShortText\=\"([a-z 0-9]+)\"\>#im', $yourOriginalString, $result) ;
print_r($result) ;

the regex function will return an array with:

   [0] => Array
        (
            [0] => <Error Code="101" Type="4" Status="NotProcessed" ShortText="Authentication refused">
        )

    [1] => Array
        (
            [0] => Authentication refused
        )

[0] is the full match [1] list the content in the matching capturing groups: each () set in your regex

Some Regex explication:

Type\=\"[0-9]+\"

Assume "Type" can change and be any numbers.

 ShortText\=\"([a-z 0-9]+)\"

Catch a string alphanumeric + space string. If you need some other stuffs, you can update like:

*[a-z 0-9\!\-]+*

catch ! and - too

#is

Are flags and ignore = caps and line break