preg_match_all 与此模式不匹配

Question

preg_match_all("/<td>\d{4}/i", $a, $b);

不匹配

<td>dddd

而

preg_match_all("/\d{4}/i", $a, $b);

工作得很好。

我错过了什么吗？

Answer 1

我假设您上面的 dddd 是数字，而不是字符 dddd。 preg_match_all 都可以工作，但第一个也可以匹配文本“

”。如果您只想要数字，则必须将它们分组在 () 中并获取该值而不是整个匹配项。

<?php

$a = "<td>1234";


$match_count = preg_match_all("/\d{4}/i", $a, $b);
print "Found: $match_count matches with /\d{4}/i\n";
print_r($b);

$match_count = preg_match_all("/<td>\d{4}/i", $a, $b);
print "Found: $match_count matches with /<td>\d{4}/i\n";
print_r($b);

#get the number in a grouping
$match_count = preg_match_all("/<td>(\d{4})/i", $a, $b, PREG_SET_ORDER);
print "Found: $match_count matches with /<td>(\d{4})/i\n";
print_r($b);


?>

输出：

Found: 1 matches with /\d{4}/i
Array
(
    [0] => Array
        (
            [0] => 1234
        )

)
Found: 1 matches with /<td>\d{4}/i
Array
(
    [0] => Array
        (
            [0] => <td>1234
        )

)
Found: 1 matches with /<td>(\d{4})/i
Array
(
    [0] => Array
        (
            [0] => <td>1234
            [1] => 1234
        )

)

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