REGEX来自一组值的前两个字符？

Question

I have a set of starting 2 alphabets as:

$arr = ['AB', 'DC', 'LF']

Problem: I need to make a regex (in PHP and TypeSript) that passes only those strings which starts with above values.

Example:

Valid:

ABwerty45^&*jk
ABwerrtty
LF%$^erftgt5234

Invalid:

TABYR56H
ab7877
Abtyu7

Any help is appreciated.

Answer 1

You could join() the array and compose a regex with an alternation like this:

<?php

$strings = <<<DATA
ABwerty45^&*jk
ABwerrtty
LF%$^erftgt5234

TABYR56H
ab7877
Abtyu7
DATA;

$arr = ['AB', 'DC', 'LF'];
$regex = '~^(?:' . join('|', $arr) . ').*~m';

if (preg_match_all($regex, $strings, $matches)) {
    print_r($matches);
}
?>

---

Which yields

Array
(
    [0] => Array
        (
            [0] => ABwerty45^&*jk
            [1] => ABwerrtty
            [2] => LF%$^erftgt5234
        )

)

---

Basically, this says:

^             # match the start of the string
(?:AB|DC|LF)  # AB or DC or LF
.*            # 0+ characters in that line