doupaxia2478 2019-07-06 14:50 采纳率: 100%
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尝试使用preg_match_all匹配包含特定类的所有图像

I try to match all images that contain a specific class by using the preg_match_all function.

This is my old code that match the all images in the content:

preg_match_all( '/<img[\s
]+.*?>/is', $content, $matches );

And this is the code that I try to made to match the images that only have a specific class but I failed:

preg_match_all( "/(<img((?!(.*?)class=['\"](.*?)comment-media(.*?)['\"](.*?)).)*>)+/is", $content, $matches );

The class that I need to search for it is: comment-media

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  • dongxin8392 2019-07-06 15:58
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    Your regex matches every img tag that has not the comment-media class. Regex101 lists this part as being "Negative Lookahead":

    (?!(.*?)class=['\"](.*?)comment-media(.*?)['\"](.*?))
    

    You'll need to remove that negative lookahead.

    The resulting regex expression will be:

    (<img(.*class=['\"](.*)comment-media(.*)['\"].*)*>)+
    

    See it in action here: https://regex101.com/r/yh7dqj/1


    What is a negative lookahead?

    A negative lookahead is used to match something not followed by something else. It always starts with (?!. For example, to match a string foo not followed by bar, one would use:

    foo(?!bar)
    

    To match foobar not followed by digits, one would use:

    # Notice the parenthesis around the part of the negative lookahead. You'll need these to use lookaheads with regex expressions.
    foobar(?!([0-9]+)).*
    

    Note that the lookahead is not part of a capturing group.

    More details are available here.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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