Check if a string contains a substring from an array of substrings and return that substring

I have an array with all German telephone area codes that is 5266 items long and looks like this:

$area_codes = array(
    '015019',
    '015020',
    '01511',
    '01512',
    '01514',
    '01515',
    '01516',
    '01517',
    '015180',
    '015181',
    '015182',
    '015183',
    '015184',
    '015185',
    'and so on'
);

I also have strings of telephone numbers that look like this:

015169999999

That is, the telephone number strings consist only of digits, without spaces, dashes, parentheses or other characters that are often used to visually structure telephone numbers.

I want to split the area code from the subscriber number and assign each to a separate variable. For the example number above, the expected result would be:

echo $area_code;
01516
echo $subscriber_number;
9999999

To identify the area code within the string, I am looping through the array of area codes:

foreach ($area_codes as $area_code) {
    if (str_starts_with($telephone_number, $area_code) == TRUE) {
        echo $area_code;
        $subscriber_number = str_replace($area_code, "", $telephone_number);
        echo $subscriber_number;
        break;
    }
}

How can I return the area code without looping?

Solutions like this require that I know where to split the string, but the area codes have different lengths.

Solution

If you want a fast lookup, you need an associative array with the area codes as the keys. For example (assuming area codes have between 4 and 6 digits):

$area_codes = array(
    '015019',
    '015020',
    '01511',
    '01512',
    '01514',
    '01515',
    '01516',
    '01517',
    '015180',
    '015181',
    '015182',
    '015183',
    '015184',
    '015185',
);

// Build an associative array
$area_lookup = [];
foreach($area_codes as $code)
    $area_lookup[$code] = 1;

function splitNumber(array $area_lookup, string $telephone_number): array
{
    for($len=4;$len<=6;$len++)
    {
        $prefix = substr($telephone_number, 0, $len);
        if(isset($area_lookup[$prefix]))
            return ['area_code' => $prefix, 'subscriber_number' => substr($telephone_number, $len)];
    }
    throw new Exception('Invalid number');
}

$res1 = splitNumber($area_lookup, '015169999999');
$res2 = splitNumber($area_lookup, '015180999999');
var_dump($res1, $res2);

Output:

array(2) {
  ["area_code"]=>
  string(5) "01516"
  ["subscriber_number"]=>
  string(7) "9999999"
}
array(2) {
  ["area_code"]=>
  string(6) "015180"
  ["subscriber_number"]=>
  string(6) "999999"
}

(Demo)