Question

我有类似的东西

$matches = array();
preg_match_all('/(`.+`)(\s+AS\s+`.+`)?/i', '`foo` AS `bar`', $matches);
print_r($matches);

结果是

Array
(
[0] => Array
    (
        [0] => `foo` AS `bar`
    )

[1] => Array
    (
        [0] => `foo` AS `bar`
    )

[2] => Array
    (
        [0] => 
    )

)

所以，问题是为什么我$matches[2][0]中没有'AS`栏'？（如果我从正则表达式中删除'？'符号，我会得到它，但我需要'？'：））

Answer 1

+之类的量词在默认情况下是贪婪的，所以如果第一个量词可以匹配它所做的一切。让它不贪婪应该做的工作：

preg_match_all('/(`.+?`)(\s+AS\s+`.+`)?/i', '`foo` AS `bar`', $matches);

顺便说一下，$matches = array();不是必需的 - 变量只由preg_match_all写入，因此不需要在之前初始化/定义。

php > preg_match_all('/(`.+?`)(\s+AS\s+`.+`)?/i', '`foo` AS `bar`', $matches);
php > print_r($matches);
Array
(
    [0] => Array
        (
            [0] => `foo` AS `bar`
        )

    [1] => Array
        (
            [0] => `foo`
        )

    [2] => Array
        (
            [0] =>  AS `bar`
        )

)

preg_match_all匹配数组

1 个答案: