Find exact string in string - PHP - php

Question

How do I find exact 2, in a string using strpos? Is it possible using strpos? The example below returns "Found" even though the match is NOT exact to what I need. I understand 2, is matching with 22,. It should return "Not Found". I am matching ID's in this example.
$string = "21,22,23,26,";
$find = "2,";
$pos = strpos($string, $find);
if ($pos !== false) {
echo "Found";
} else {
echo "Not Found";
}

Answer 1

Unless the string is enormous, make an array and search it:
$string = "21,22,23,26,";
$arr = explode(",", $string);
// array_search() returns its position in the array
echo array_search("2", $arr);
// null output, 2 wasn't found
Actually, in_array() is probably faster:
// in_array() returns a boolean indicating whether it is found or not
var_dump(in_array("2", $arr));
// bool(false), 2 wasn't found
var_dump(in_array("22", $arr));
// bool(true), 22 was found
This will work as long as your string is a comma-delimited list of values. If the string is really long, making an array may be wasteful of memory. Use a string manipulation solution instead.
Addendum
You didn't specify, but if by some chance these strings came from a database table, I would just add that the appropriate course of action would be to properly normalize it into another table with one row per id rather than store them as a delimited string.

Answer 2

Try with explode and in_array
Example:
$string = "21,22,23,26,";
$string_numbers = explode(",", $string);
$find = 2;
if (in_array($find, $string_numbers)) {
echo "Found";
} else {
echo "Not Found";
}

Answer 3

You can use preg_match if you want to avoid arrays.
$string = "21,22,23,26,";
$find = '2';
$pattern = "/(^$find,|,$find,|,$find$)/";
if (0 === preg_match($pattern, $string)) {
echo "Not Found";
} else {
echo "Found";
}
This will find your id at beginning, middle or at the end of the string. Of course, I am assuming $string does not contain characters other than numbers and commas (like spaces).