How to write a function that removes all characters from a string except numbers in php

You can name the function something like get_digits_only.

Here’s an example implementation:

function get_digits_only($input) {
    return preg_replace('/\D/', '', $input);
}

// Example usage:
$string = "Phone: +1 (800) 555-1234";
$digits = get_digits_only($string);
echo $digits; // Output: 18005551234

The name reflects the function’s purpose: extracting only digits from a string.