Say I have the following: preg_match("/ESP[0-9]?[0-9]/", $devid)
I want to match data such as the following:$devid = "ESP1"$devid = "ESP10"$devid = "ESP78"
However, I don't want the string to contain anything that isn't matched in the regex. For example: $devid = "ESP100" would return ESP10$devid = "ESP10234234" would return ESP10$devid = "ESP78hello" would return ESP78
...and if there isn't a match, returning null (or equivalent).
In a way, I want to detect where preg_match finishes, and then remove the rest.
You can use a third argument in preg_match like:
preg_match('/ESP\d\d?/', $string, $matches);
var_dump($matches[0] ?? NULL);
In case nothing is found NULL will be output.
Edit(cars10m):
From testing in rextester.com I found that $matches is returned as an array of length 0, when nothing is found, see here: http://rextester.com/UUM57869
You can use preg_replace with a capture group:
$devid = preg_replace('/^(ESP\d{1,2}+).+/', '$1', $devid);
This regex matches & captures the text that we want to keep in group #1 and in replacement we put back $1.
or without the capture group use match reset \K:
$devid = preg_replace('/^ESP\d{1,2}+\K.+/', '', $devid);
This regex matches text that we want to keep and then using \K we reset match info. In replacement we just use empty string.
Note that {1,2}+ matches between 1 and 2 times, as many times as possible, without giving back.
I believe you need the word boundary \b.
preg_match("/\bESP\d{1,2}\b/", $devid, $match);
The word boundary makes sure it matches a word that starts with ESP and ends with one or two digits.