[RESOLVED] Can't echo an int variable when its set to 0???? Wierd!!!

jsauve

I'm working on a programming assignment: converting hex to decimal and vice versa. I know there's built in functions for this, but I'm supposed to use repeated division and multiplication to achieve converting from one base to another.

Anyway, I don't need help with the overall project. I just have a few helper functions I'm trying to put together, one of which is a hex digit to integer converter. Not very elegant, but it works....kinda.

//function hex2int() takes a hexadecimal digit and returns an int
	function hex2int($var) {
		if ($var == "0") {$final = 0;}
		else if ($var == "1") {$final = 1;}
		else if ($var == "2") {$final = 2;}
		else if ($var == "3") {$final = 3;}
		else if ($var == "4") {$final = 4;}
		else if ($var == "5") {$final = 5;}
		else if ($var == "6") {$final = 6;}
		else if ($var == "7") {$final = 7;}
		else if ($var == "8") {$final = 8;}
		else if ($var == "9") {$final = 9;}
		else if (($var == "a") || ($var == "A")) {$final = 10;}
		else if (($var == "b") || ($var == "B")) {$final = 11;}
		else if (($var == "c") || ($var == "C")) {$final = 12;}
		else if (($var == "d") || ($var == "D")) {$final = 13;}
		else if (($var == "e") || ($var == "E")) {$final = 14;}
		else if (($var == "f") || ($var == "F")) {$final = 15;}
		else echo "Error: a single hexadecimal digit is required.";
		return $final;
	}

I then echo $final to the browser. It works great, but 0 doesn't echo anything! What's going on here?

NogDog

I copied your function and ran the command echo hex2int(0);, and it output '0' as expected. How are you doing the output?

Scriptmaker

Try

echo $_POST['num_input'];

to see what's going in.

Also, if the programming assignment doesn't specifically say to use a bunch of if...elseif statements, http://www.php.net/switch is a little cleaner and easier on the wrists.

Weedpacket

Scriptmaker wrote:
http://www.php.net/switch is a little cleaner and easier on the wrists.

If I couldn't use the existing function I'd be more inclined to use a static array lookup.

jsauve

NogDog,

It looks like you're passing it an int, not a string, right? Maybe that's why its working for you?

Here's the whole file, so you can see how I'm doing for output:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Hex to Int test</title>
</head>

<body>
<?php
	//function hex2int() takes a hexadecimal digit and returns an int
	function hex2int($var) {
		if ($var == "0") {$var2 = 0;}
		else if ($var == "1") {$var2 = 1;}
		else if ($var == "2") {$var2 = 2;}
		else if ($var == "3") {$var2 = 3;}
		else if ($var == "4") {$var2 = 4;}
		else if ($var == "5") {$var2 = 5;}
		else if ($var == "6") {$var2 = 6;}
		else if ($var == "7") {$var2 = 7;}
		else if ($var == "8") {$var2 = 8;}
		else if ($var == "9") {$var2 = 9;}
		else if (($var == "a") || ($var == "A")) {$var2 = 10;}
		else if (($var == "b") || ($var == "B")) {$var2 = 11;}
		else if (($var == "c") || ($var == "C")) {$var2 = 12;}
		else if (($var == "d") || ($var == "D")) {$var2 = 13;}
		else if (($var == "e") || ($var == "E")) {$var2 = 14;}
		else if (($var == "f") || ($var == "F")) {$var2 = 15;}
		else {
			echo "Error: a single hexadecimal digit is required.<br />";
			echo "The data type of the result is: " . gettype($var2);
		}
		return $var2;
	}

if ($_POST[num_input]) {
	$temp = $_POST[num_input];
	$result = hex2int($temp);
}

?>
<!-- BEGIN form.  -->
<form id="conversion" name="conversion" method="post" action="<?php $_SERVER['PHP_SELF']; ?>">
  <h3 style="font-family:verdana;">Hexadecimal Digit -> Integer Converter</h3>
  <br />
  <p>
  <label>Enter a hexadecimal digit (0 - F) to convert to an integer:
    <input type="text" name="num_input" id="num_input" />
  </label>
    <input type="submit" name="convert" id="convert" value="Convert!" />
  </p>
  <p>Your integer: <?php echo $result; //display $result?></p>
</form>
<!-- END form. -->
</body>
</html>

jsauve

Scriptmaker,

Cool! I didn't know you could switch on strings! I'm used to C++ not liking strings for switches. Good to know!

jsauve

Weedpacket,

So you're saying create an array, plop my int values into it, then just pull em' out by their indexes depending on which one I need? Sehr schön! 😃

NogDog

It's not the function that is the problem, it's this if statement:

if ($_POST[num_input]) {

It will evaluate to false if $_POST['num_input'] is boolean false, 0, "0", "" (empty string) or NULL. (By the way, you should quote the array index, otherwise you are creating a self-defined constant, which will throw a notice-level run-time warning.) A better test would be:

if(isset($_POST['num_input'])) {

jsauve

Ahhhhhh.....

Awesome. It worked. NogDog, you're one bad muthatrucka. Thanks!

NogDog

PS: If you want a simple(?) one-liner to do the inverse (convert a decimal integer to a hexidecimal string):

function int2hex($var) {
   return sprintf('%X', (int)$var);
}

🙂