Regular Expression:Why doesn't this work?

[loci]

/^(20)(?(1)(0[7-9]|[^0]\d)|(21)\d\d)$/

I am trying to get this conditional expression to match dates between 2007 and 2199.

If i try 2007, or anything of the form 20 , it works, when i try any year of the form 21 , it does not work

Could you help me with this? it would be greatly appreciated.

Thanks for your attention

Oh and the "/d" seems to be showing up in the post only as "d" but the backslash is in my code.

[NogDog]

Perhaps (untested):

$pattern = '/^2(00[7-9])|(0[1-9]\d)|(1\d\d)$/';

Though frankly I think I'd do:

if(ctype_digit($value) and $value >= 2007 and $value <= 2199)
{

[loci]

I really wanted to find out what was wrong with what i did, just to learn something from it.

Your pattern works , and i intend it to use it, thanks for your response, i appreciate it.

Thanks also for your suggestion, why would you take that rout though, is there an advantage?

Thanks a million.

[NogDog]

I'd probably do it the second way because it's easier to read and thus easier to maintain, while I doubt either method has a significant speed advantage (though if I had to bet, I'd put a small wager on the "ctype()...etc." method being a bit faster).

[Weedpacket]

It depends on the test data, but here's a test:

//Building test data: one hundred thousand numbers between 0 and 4000.
$nums = array();
for($i=0; $i<100000; ++$i)
{
	$nums[] = mt_rand(0,4000);
}
//A few have letters as well as digits.
for($i=0; $i<10; ++$i)
{
	$nums[$i].='fnord';
}
for($i=0; $i<10; ++$i)
{
	$nums[$i]='fnord'.$nums[$i];
}


$start1 = microtime(true);
$found1=0;
foreach($nums as $num)
	if(preg_match('/^2(00[7-9])|(0[1-9]\d)|(1\d\d)$/', $num))
		++$found1;
$start2 = $end1 = microtime(true);
$found2 = 0;
foreach($nums as $num)
	if(ctype_digit($num) and $num >= 2007 and $num <= 2199)
		++$found2;
$start3 = $end2 = microtime(true);
$found3 = 0;
foreach($nums as $num)
	if($num >= 2007 and $num <= 2199 && ctype_digit($num))
		++$found3;
$end3 = microtime(true);

echo "preg_match timing: ".($end1-$start1)." seconds: matched $found1 items\n";
echo "ctype+range timing: ".($end2-$start2)." seconds: matched $found2 items\n";
echo "range+ctype timing: ".($end3-$start3)." seconds: matched $found3 items\n";

Typical results include:

preg_match timing: 3.1900889873504639 seconds: matched 16712 items
ctype+range timing: 1.0025169849395752 seconds: matched 4766 items
range+ctype timing: 0.14614200592041016 seconds: matched 4766 items

Note the discrepancy in the number of items matched. The regexp should have been written "/^{2((00[7-9])|(0[1-9]\d)|(1\d\d))$/"} - which just goes to prove NogDog's point about legibility and maintainability.