CODEWITHSUNDEEP
php
underrated
underrated

Reputation: 55

Check if the string is followed by integers

So I want to check if my input field contains a specific characters and integers. The only value I accept is like this 'KM00000'. It must starts with KM and followed by 5 characters of integers.To check if the string starts with the letter 'KM', I can do this

if (substr($fm_id, 0, 2) !== "KM") {
     die("<script>alert('ID is in the wrong format.');
     window.history.back();</script>");
}

But I don't know how to check if the following characters after the letter "KM" is followed by an integer or not

Upvotes: 1

Views: 35

Answers (1)

Sammitch
Sammitch

Reputation: 32232

function check_classic($input) {
    if( strlen($input) !== 7 ) {
        return false;
    }
    if( substr($input, 0, 2) !== 'KM' ) {
        return false;
    }
    for( $i=0,$c=5,$s=substr($input, 2, 5); $i<$c; ++$i ) {
        $ord = ord($s[$i]);
        // ord('0') == 48, ord('9') == 57
        if( $ord < 48 || $ord > 57 ) {
            return false;
        }
    }
    return true;
}

function check_regex($input) {
    return preg_match('/^KM\d{5}$/', $input);
}

$inputs = [ 'KM12345', 'KM1234', 'KM123456', 'KM1234v' ];

foreach($inputs as $input) {
    printf("Classic: %-8s %s\n", $input, check_classic($input) ? 'true' : 'false');
    printf("Regex:   %-8s %s\n", $input, check_regex($input)   ? 'true' : 'false');
}

Output:

Classic: KM12345  true
Regex:   KM12345  true
Classic: KM1234   false
Regex:   KM1234   false
Classic: KM123456 false
Regex:   KM123456 false
Classic: KM1234v  false
Regex:   KM1234v  false

While the regular expression is certainly less lines of code, it's a different domain-specific language to learn. Plus I think it's important to show the "classic" approach to solving the problem as well, which is roughly what the regular expression is doing under the hood.

Ref:

Upvotes: 2

Related Questions