dousu8767 2015-11-05 10:42
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php preg_match_all简单正则表达式返回空值

I need to extract a predefined set of hashtags from a blob of text, then extract what number follows right after it if any. Eg. I'd need to extract 30 from "Test string with #other30 hashtag". I assumed preg_match_all would be the right choice.

Some test code:

$hashtag = '#other';
$string  = 'Test string with #other30 hashtag';
$matches = [];
preg_match_all('/' . $hashtag . '\d*/', $string, $matches);
print_r($matches);

Output:

Array
(
    [0] => Array
        (
            [0] => #other30
        )
)

Perfect... Works as expected. Now to extract the number:

$string = $matches[0][0]; // #other30
$matches = [];
preg_match_all('/\d*/', $string, $matches);
print_r($matches);

Output:

Array
(
    [0] => Array
        (
            [0] =>
            [1] =>
            [2] =>
            [3] =>
            [4] =>
            [5] =>
            [6] => 30
            [7] =>
        )
)

What? Looks like it's trying to match every character?

I'm aware of some preg_match_all related answers (one, two), but they all use a parenthesized subpattern. According to documentation - it is optional.

What am I missing? How do I simply get all matches into an array that match such a basic regex like /\d*/ There doesn't seem to be a more appropriate function in php for that.

I never thought I'd be scratching my head with such a basic thing in PHP. Much appreciated.

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4条回答 默认 最新

  • douxuanou2787 2015-11-05 10:47
    关注

    You need to replace:

    preg_match_all('/\d*/', $string, $matches);
    

    with:

    preg_match_all('/\d+/', $string, $matches);
    

    Replace * with +

    Because

    * Match zero or more times.

    + Match one or more times.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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