[RESOLVED] my pad function fails to pad integers with a leading zero

[ppowell]

Could someone please spot-check this function and tell me why it never, ever, pads an integer with a leading zero when I want it to?

This function fails in PHP 4.3.8, 4.4.1 and 4.3.9

Thanx
Phil

if (!function_exists('pad')) {
 /**
  * Pad a string.  Use str_pad() as default unless the input string value is larger than the amount of padding to take place due to str_pad() rules (PHP needs to update this!!)
  *
  * @access public
  * @param mixed $input (reference)
  * @param int $offset Number of times to repeat padding character
  * @param char $padChar Character to pad with
  * @param int $padConstant (optional) PAD_CONSTANT constant value (e.g. STR_PAD_LEFT, STR_PAD_RIGHT, etc.)
  * @return mixed $paddedString
  * @link http://us3.php.net/manual/en/function.str-pad.php
  * @see link regarding usage of str_pad() function
  */
 function &pad(&$input, $offset, $padChar, $padConstant = STR_PAD_RIGHT) {
	define(PAD_CONSTANT, $padConstant);																	// MAKE INTO CONSTANT FOR NAMING CONVENTION
	if ((int)$offset > 0 && (int)$offset >= strlen($input)) return str_pad($input, $offset, $padChar, PAD_CONSTANT);	// USE str_pad() BY DEFAULT IF RULES APPLY
	if ((int)$offset === 0 || strlen($input) == 0 || !isset($padChar) || strlen($padChar) < 1) return $input;			// NOTHING TO PAD
	switch(PAD_CONSTANT) {
	 case STR_PAD_LEFT:
	  for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input";
	  break;
	 case STR_PAD_RIGHT:
	  for ($i = 1; $i <= $offset; $i++) $input = "$input$padChar";
	  break;
	 case STR_PAD_BOTH:
	  for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input$padChar";
	  break;
	 default: // DO NOTHING
	  break;
	}
	return $input;
 }
}

[Installer]

Because when you call it with something like "echo pad(8, 1, '0', STR_PAD_LEFT)" your function calls "str_pad()" which returns "8", as it should.

You might better ask yourself "Why can't I understand the usage of str_pad()?" and "Why did I turn off error reporting again?".

See this thread.

[ppowell]

Right, that's my original thread, and it still makes no sense to me. Is it one of those deals where PHP looks at "8" and says "hey that's not a string that's an integer so I won't pad it" even though strlen("8") = 1 anyway?

Guess, what? I still don't get it!

Phil

[NogDog]

For one thing, if you're going to define a function using return-by-reference, you cannot return an expression; you can only return a variable. (And if you don't have some specific technical reason to be defining your function as return-by-reference, you should not be doing it anyway.)

[Weedpacket]

Installer wrote:

pad(8, 1, '0', STR_PAD_LEFT)

ppowell wrote:

Is it one of those deals...

No, it's one of those deals where PHP looks at "8" and says "I don't need to pad that because you asked for a one-character-long string and '8' is already one character long."

[bradgrafelman]

Once again, Weedpacket's post here explains the problem in a great deal of depth.

The 2nd parameter of [man]str_pad/man is the desired length of the string. If you put a 10 for this parameter, PHP will pad the string you give it until the string is 10 characters in length. If the string is already 10 characters or more, PHP will do nothing to it.

Example:

echo str_pad('123', 10, '0', STR_PAD_LEFT); // 0000000123
echo str_pad('123456789123456789', 10, '0', STR_PAD_LEFT); // 123456789123456789

[Installer]

That's at least a half-dozen cogent explanations so far, not counting mine, which was too heavy on the math (or that branch of math known as "grade-school arithmetic").

[ppowell]

of strings?

[ppowell]

bradgrafelman wrote:

Once again, Weedpacket's post here explains the problem in a great deal of depth.

The 2nd parameter of [man]str_pad/man is the desired length of the string. If you put a 10 for this parameter, PHP will pad the string you give it until the string is 10 characters in length. If the string is already 10 characters or more, PHP will do nothing to it.

Example:

echo str_pad('123', 10, '0', STR_PAD_LEFT); // 0000000123
echo str_pad('123456789123456789', 10, '0', STR_PAD_LEFT); // 123456789123456789

Right and that's the problem, I might have a 10-character string that I WANT to pad with 10 successive zeroes, hence I do the default check via str_pad() first and then do my own afterwards if it doesn't produce the right results.

Bottom line is that my pad() function will have to receive "8" as a string instead of as an integer, but then again, PHP makes this whole thing so confusing I don't know how to force "8" to become "08", plain and simple, unless I hack it this way:

<?= date('m', strtotime('8/1/2006')); ?>

Java makes this so much easier, even to someone that was a math major in college 3.0 GPA who understands grade-school math better than Installer understands the real problem.

Phil

[Installer]

...how to force "8" to become "08"...

$arr = array(8, '8');
foreach ($arr as $val) {
    echo str_pad($val, 2, '0', STR_PAD_LEFT) . '<br />';
}

Displays:
08
08

[ppowell]

I wish you had explained it, but your solution works.. it sppears it works because str_pad() has a fundamental flaw that refuses to pad a string if the offset is the same length as the string itself. My pad() function now works perfectly, so thanx!

if (!function_exists('pad')) {
 /**
  * Pad a string.  Use str_pad() as default unless the input string value is larger than the amount of padding to take place due to str_pad() rules (PHP needs to update this!!)
  *
  * @access public
  * @param mixed $input (reference)
  * @param int $offset Number of times to repeat padding character
  * @param char $padChar Character to pad with
  * @param int $padConstant (optional) PAD_CONSTANT constant value (e.g. STR_PAD_LEFT, STR_PAD_RIGHT, etc.)
  * @return mixed $paddedString
  * @link http://us3.php.net/manual/en/function.str-pad.php
  * @see link regarding usage of str_pad() function
  */
 function &pad(&$input, $offset, $padChar, $padConstant = STR_PAD_RIGHT) {
	define(PAD_CONSTANT, $padConstant);																	// MAKE INTO CONSTANT FOR NAMING CONVENTION
	if ((int)$offset > 0 && (int)$offset > strlen($input)) return str_pad($input, $offset, $padChar, PAD_CONSTANT);	// USE str_pad() BY DEFAULT IF RULES APPLY
	if ((int)$offset === 0 || strlen($input) == 0 || !isset($padChar) || strlen($padChar) < 1) return $input;			// NOTHING TO PAD
	switch(PAD_CONSTANT) {
	 case STR_PAD_LEFT:
	  for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input";
	  break;
	 case STR_PAD_RIGHT:
	  for ($i = 1; $i <= $offset; $i++) $input = "$input$padChar";
	  break;
	 case STR_PAD_BOTH:
	  for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input$padChar";
	  break;
	 default: // DO NOTHING
	  break;
	}
	return $input;
 }
}

No grade-school math knowledge required.

Phil

[Weedpacket]

ppowell wrote:

I might have a 10-character string that I WANT to pad with 10 successive zeroes

$string = "ten chars!";
$padded_string = "0000000000".$string;

Done: a ten-character string padded with 10 successive zeroes. On the left, even.

ppowell wrote:

and then do my own afterwards if it doesn't produce the right results.

Well, that IS a bug in PHP - it only does what you tell it to do; obviously it should be able to figure out what you want it to do and then write itself.

ppowell wrote:

better than Installer understands the real problem.

You're the one who's insisting that

(PHP needs to update this!!)

I suspect Installer is quite familiar with what the real problem here is.

Incidentally, how would you do this in Java? I suspect genuine working code that does what you want would be easier to understand than your explanations.

[bradgrafelman]

I don't get this entire thread... why should this mess of code:

if (!function_exists('pad')) { 
/** 
  * Pad a string.  Use str_pad() as default unless the input string value is larger than the amount of padding to take place due to str_pad() rules (PHP needs to update this!!) 
  * 
  * @access public 
  * @param mixed $input (reference) 
  * @param int $offset Number of times to repeat padding character 
  * @param char $padChar Character to pad with 
  * @param int $padConstant (optional) PAD_CONSTANT constant value (e.g. STR_PAD_LEFT, STR_PAD_RIGHT, etc.) 
  * @return mixed $paddedString 
  * @link http://us3.php.net/manual/en/function.str-pad.php 
  * @see link regarding usage of str_pad() function 
  */ 
function &pad(&$input, $offset, $padChar, $padConstant = STR_PAD_RIGHT) { 
    define(PAD_CONSTANT, $padConstant);                                                                    // MAKE INTO CONSTANT FOR NAMING CONVENTION 
    if ((int)$offset > 0 && (int)$offset > strlen($input)) return str_pad($input, $offset, $padChar, PAD_CONSTANT);    // USE str_pad() BY DEFAULT IF RULES APPLY 
    if ((int)$offset === 0 || strlen($input) == 0 || !isset($padChar) || strlen($padChar) < 1) return $input;            // NOTHING TO PAD 
    switch(PAD_CONSTANT) { 
     case STR_PAD_LEFT: 
      for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input"; 
      break; 
     case STR_PAD_RIGHT: 
      for ($i = 1; $i <= $offset; $i++) $input = "$input$padChar"; 
      break; 
     case STR_PAD_BOTH: 
      for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input$padChar"; 
      break; 
     default: // DO NOTHING 
      break; 
    } 
    return $input; 
} 
}

replace this code?

str_pad('12', 3, '0', STR_PAD_LEFT);

[ppowell]

bradgrafelman wrote:

I don't get this entire thread... why should this mess of code:

if (!function_exists('pad')) { 
/** 
  * Pad a string.  Use str_pad() as default unless the input string value is larger than the amount of padding to take place due to str_pad() rules (PHP needs to update this!!) 
  * 
  * @access public 
  * @param mixed $input (reference) 
  * @param int $offset Number of times to repeat padding character 
  * @param char $padChar Character to pad with 
  * @param int $padConstant (optional) PAD_CONSTANT constant value (e.g. STR_PAD_LEFT, STR_PAD_RIGHT, etc.) 
  * @return mixed $paddedString 
  * @link http://us3.php.net/manual/en/function.str-pad.php 
  * @see link regarding usage of str_pad() function 
  */ 
function &pad(&$input, $offset, $padChar, $padConstant = STR_PAD_RIGHT) { 
    define(PAD_CONSTANT, $padConstant);                                                                    // MAKE INTO CONSTANT FOR NAMING CONVENTION 
    if ((int)$offset > 0 && (int)$offset > strlen($input)) return str_pad($input, $offset, $padChar, PAD_CONSTANT);    // USE str_pad() BY DEFAULT IF RULES APPLY 
    if ((int)$offset === 0 || strlen($input) == 0 || !isset($padChar) || strlen($padChar) < 1) return $input;            // NOTHING TO PAD 
    switch(PAD_CONSTANT) { 
     case STR_PAD_LEFT: 
      for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input"; 
      break; 
     case STR_PAD_RIGHT: 
      for ($i = 1; $i <= $offset; $i++) $input = "$input$padChar"; 
      break; 
     case STR_PAD_BOTH: 
      for ($i = 1; $i <= $offset; $i++) $input = "$padChar$input$padChar"; 
      break; 
     default: // DO NOTHING 
      break; 
    } 
    return $input; 
} 
}

replace this code?

str_pad('12', 3, '0', STR_PAD_LEFT);

It shows a considerable lack of social skill to call someone else's code a "mess" that happens to work the way he wants it to work and the requirements of the project. I don't insult your code, please don't insult mine. This thread is closed, drop it.

[Weedpacket]

bradgrafelman wrote:

I don't get this entire thread... why should this mess of code:

That's what we're all wondering. Understanding that 3-2=1 appears to be a hurdle, though.

ppowell wrote:

...call someone else's code a "mess"...

Perhaps it's a typo for "mass", but it's still a valid technical judgement: badly written code is expensive to develop, maintain, fix, and execute.

ppowell wrote:

that happens to work the way he wants it to work and the requirements of the project.

Said requirements apparently including

This function fails in PHP 4.3.8, 4.4.1 and 4.3.9

[bradgrafelman]

ppowell wrote:

It shows a considerable lack of social skill to call someone else's code a "mess" that happens to work the way he wants it to work and the requirements of the project. I don't insult your code, please don't insult mine.

Wasn't trying to offend or insult... perhaps my word choice was a bit poor. By "mess", I simply meant extremely longer than necessary (and therefore probably less efficient memory/CPU-wise).

ppowell wrote:

This thread is closed, drop it.

Once again, the mistake here is mine. I thought everyone who came to this forum with questions were looking for ways to improve their code and understanding of PHP. Sorry for that misunderstanding... I'll stop replying to this thread.