php regex - find string within string

Question

I need to identify a string that can contain 1- 6 # symbols inside another string and retrun the start position of the substring and the substring itself.

for example:

example ## string => [strpos=> 9, stren => 2]

so far I have this:

/["#"]{1,6}/gm

Can anyone help?

@PhilippSander ... just out of curiosity, how would you define a substring then? — CD001
– CD001, Commented Jul 13, 2018 at 15:53
Note you should not use g modifier in PHP regex, and m is not necessary here since there is no ^ and $. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 13, 2018 at 15:53
And, what do you intend to do with the offset information ? And, you won't get a length value in any php regex functions. Unless this is for educational purposes, maybe explain what you're trying to do. — user557597
– user557597, Commented Jul 13, 2018 at 16:00

Wiktor Stribiżew · Accepted Answer · 2018-07-13 15:48:39Z

3

You may use preg_match (or preg_match_all to get multiple matches) with the PREG_OFFSET_CAPTURE argument:

$str = "example ## string";
if (preg_match('~#{1,6}~', $str, $m, PREG_OFFSET_CAPTURE)) {
    print_r($m);
}

See PHP preg_match reference:

PREG_OFFSET_CAPTURE
If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the value of matches into an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.

See the PHP demo, output:

Array
(
    [0] => Array
        (
            [0] => ##
            [1] => 8
        )

)

answered Jul 13, 2018 at 15:48

Wiktor Stribiżew

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