PHP: Check binary string, running into errors here..

Question

I'm using this function to check if binary is correct, I know it looks sloppy.. I'm not sure how to write the function that well.. but it doesn't seem to work!

If binary = 10001000 it says malformed, even though it's not.. what is wrong in my function?..

function checkbinary($bin) {
    $binary = $bin;
    if(!strlen($binary) % 8 == 0){
        return 1;
    }
    if (strlen($binary) > 100) { 
        return 1;
    } 
    if (!preg_match('#^[01]+$#', $binary)){ //Tried without !
        return 1;
    } 
    if (!is_numeric($binary)) {
        return 1;   
    }
}

if (checkbinary("10001000") != 1) {
  echo "Correct";
} else {
  echo "Binary incorrect";
}

Why does this function always say 10001000 is incorrect?

Answer 1

How about using PHP's built-in is_binary function. It must be better implementation ofcourse.

Answer 2

if(!strlen($binary) % 8 == 0){ should be

if( strlen($binary) % 8 !== 0 ){

edit and btw: Since you're already using preg_match() you can simplify/shorten the function to

function checkbinary($binary) {
  return 1===preg_match('#^(?:[01]{8}){0,12}$#', $binary);
}

This allows 0 - 12 groups of 8 0/1 characters which includes all the tests you currently have in your function:

• strlen()%8 is covered by {8} in the inner group
• strlen() > 100 is covered by {0,12} since any string longer than 8*12=96 characters would trigger either the first if or the >100 test
• 0/1 test is obvious
• is_numeric is kinda superfluous

edit2: The name checkbinary might not be a perfect choice for the function. I wouldn't necessarily expect it to check for 8bit/byte alignment and strlen()<=100.

Answer 3

function checkbinary($bin) {
    return preg_match('#^[01]+$#', $bin);
}

Some tests: http://www.ideone.com/3D9SQetX and http://www.ideone.com/1HCCtxVV.

Answer 4

I'm not entirely sure what you're attempting to achieve, but you might be able to get there via the following...

if($binaryString == base_convert($binaryString, 2, 2))...

In essence, this is comparing the results of a conversion from binary to binary - hence if the resultant output is identical, the input must be a valid binary string.