ereg and preg_match give a different result

[AP81]

Hi,

 

I'm working on some old code (someone else wrote) and have to replace old the old 'ereg' functions to preg_match.  As we are moving to PHP 5.3 the ereg functions are deprecated.

 

The funny thing is that these two pieces of code produce different output.  One uses ereg and the other preg_match.  Any reasons as to why? 

 

The code below produces a different size array of matches for $amt3 and $amt4.  I can write a work around but am just wondering why the output is different, as all documentation I have read state that ereg and preg_match are almost identical in the result they produce.

 

$amt1 = '$100.00';
$amt2 = '100.00';
$amt3 = '$100';
$amt4 = '100';

    function parseFromString($amount) {

        if (!preg_match('/^([A-Z]{1,3})?(\$)?([0-9]+)((\.)([0-9]+))?$/', $amount, $regs)) {
            return null;
        }
        var_dump($regs);
    }

function parseFromString1($amount) {
	if (!ereg('^([A-Z]{1,3})?(\$)?([0-9]+)((\.)([0-9]+))?$', $amount, $regs)) {
		return null;
	}
	var_dump($regs);
}

parseFromString($amt1);
parseFromString($amt2);
parseFromString($amt3);
parseFromString($amt4);

echo "\n\n==============================\n\n";

parseFromString1($amt1);
parseFromString1($amt2);
parseFromString1($amt3);
parseFromString1($amt4);

 

Output:

 

array(7) {
  [0]=>
  string(7) "$100.00"
  [1]=>
  string(0) ""
  [2]=>
  string(1) "$"
  [3]=>
  string(3) "100"
  [4]=>
  string(3) ".00"
  [5]=>
  string(1) "."
  [6]=>
  string(2) "00"
}
array(7) {
  [0]=>
  string(6) "100.00"
  [1]=>
  string(0) ""
  [2]=>
  string(0) ""
  [3]=>
  string(3) "100"
  [4]=>
  string(3) ".00"
  [5]=>
  string(1) "."
  [6]=>
  string(2) "00"
}
array(4) {
  [0]=>
  string(4) "$100"
  [1]=>
  string(0) ""
  [2]=>
  string(1) "$"
  [3]=>
  string(3) "100"
}
array(4) {
  [0]=>
  string(3) "100"
  [1]=>
  string(0) ""
  [2]=>
  string(0) ""
  [3]=>
  string(3) "100"
}


==============================

array(7) {
  [0]=>
  string(7) "$100.00"
  [1]=>
  bool(false)
  [2]=>
  string(1) "$"
  [3]=>
  string(3) "100"
  [4]=>
  string(3) ".00"
  [5]=>
  string(1) "."
  [6]=>
  string(2) "00"
}
array(7) {
  [0]=>
  string(6) "100.00"
  [1]=>
  bool(false)
  [2]=>
  bool(false)
  [3]=>
  string(3) "100"
  [4]=>
  string(3) ".00"
  [5]=>
  string(1) "."
  [6]=>
  string(2) "00"
}
array(7) {
  [0]=>
  string(4) "$100"
  [1]=>
  bool(false)
  [2]=>
  string(1) "$"
  [3]=>
  string(3) "100"
  [4]=>
  bool(false)
  [5]=>
  bool(false)
  [6]=>
  bool(false)
}
array(7) {
  [0]=>
  string(3) "100"
  [1]=>
  bool(false)
  [2]=>
  bool(false)
  [3]=>
  string(3) "100"
  [4]=>
  bool(false)
  [5]=>
  bool(false)
  [6]=>
  bool(false)
}

[xyph]

preg_match() won't create array keys if it doesn't need to. It also returns an empty string instead of FALSE on capturing groups with no return.

 

You can quite easily modify the array to match your old ereg return.