PHP: Simple regular expression to match exact length of digits

Question

I am trying a simple regex to match exactly 5 digits from a string. However, this pattern matches for 5 and more than 5.

preg_match_all('#[0-9]{5}+#', 'one two 412312 three (51212 four five)', $matches);
print_r($matches);

Result:

Array(
    [0] => Array
    (
        [0] => 41231
        [1] => 51215
    )
)

I need it to match exactly 5 digits.

Thanks.

Answer 1

You can use word boundaries here and remove the + quantifier after the range operator.

preg_match_all('~\b\d{5}\b~', $str, $matches);

As stated in the comments, if you need to match the five digits in a51212a but not 412312 you can use a combination of lookaround assertions.

preg_match_all('~(?<!\d)\d{5}(?!\d)~', $str, $matches);

Answer 2

Try this:

preg_match_all('(\b\d{5}\b)', 'one two 412312 three (51212 four five)', $matches);
print_r($matches);

It matches every group of 5 digits.

Answer 3

您可以为此使用前行和-后： (?<!\\d)[0-9]{5}(?!\\d)