Regular expressions: how to match numbers?

问题

I want to use regular expressions to match numbers like these:

58158
60360
98198

That is in the format ABCAB.

I use code below to match ABAB:

(([\d]){1,}([\d]){1,})\1{1,}

such as 5858 but how to match ABCAB(58158)?

回答1:

For numbers in the format ABCAB:

(\d)(\d)\d\1\2

This places no restriction on A=B=C. Use negative look-ahead for A!=B!=C:

(\d)(?!\1)(\d)(?!\1|\2)\d\1\2

Edit:

There is no boundary matching so 58158 will be matched in 36958158:

$num=36958158;
preg_match('/(\d)(?!\1)(\d)(?!\1|\2)\d\1\2/',$num,$match);
echo ">>> ".$match[0];

>>> 58158

回答2:

To match integers in the form ABCAB, use \b(\d\d)\d(\1)\b.

\b is a word boundary and \1 references the first group.

Example (in JavaScript so that it can be tested in the browser but it works in most regex solutions) :

var matches = '58158 22223 60360 98198 12345'.match(/\b(\d\d)\d(\1)\b/g);

gives

["58158", "60360", "98198"]

来源：https://stackoverflow.com/questions/15346178/regular-expressions-how-to-match-numbers