A PHP function to check if a string is an integer

is_integer.php

/**
 *  This function takes a string and tells you
 *  if the string represents an integer. 
 *  All characters of the string must be digits,
 *  and there cannot be any leading zeros.
 *
 *  @param String $string The string to check.
 *  @return Boolean
 */
function is_this_string_an_integer($string) {

    // Assume from the start that the string IS an integer.
    // If we hit any problems, we'll bail out and say it's NOT an integer.
    $is_integer = true;

    // Convert the string into an array of characters.
    $array_of_chars = str_split($string);

    // If there are no characters, we don't have an integer.
    if (empty($array_of_chars)) {
    	$is_integer = false;
    }

    // If the first character is a zero, we don't have an integer.
    // Instead, we have a string with leading zeros.
    if ($is_integer && $array_of_chars[0] == '0') {
    	$is_integer = false;
    }
    
    // If we still think it might be an integer, 
    // step through each char and see if it's a legitimate digit.
    if ($is_integer) {
        foreach ($array_of_chars as $i => $char) {
    
            // Use PHP's ctype_digit() function to see if this 
            // character is a digit. If not, we can bail.
            if (!ctype_digit($char)) { 
      	        $is_integer = false;
      	        break;
      	    }
      	    
        }

    }
	
    // Finally, do we have an integer string or not?
    return $is_integer;
  
}