preg_match() behaving strange? - php

Question

I want to compare two strings against url:
$reg1 = "/(^(((www\.))|(?!(www\.)))domain\.com\/paramsindex\/([a-z]+)\/([a-z]+)\/((([a-z0-9]+)(\-[a-z0-9]+){0,})(\/([a-z0-9]+)(\-[a-z0-9]+){0,}){0,})|()\/?$)/";
$reg2 = "/(^(((www\.))|(?!(www\.)))domain\.com\/paramsassoc\/([a-z]+)\/([a-z]+)\/((([a-z0-9]+)(\-[a-z0-9]+){0,})(\/([a-z0-9]+)(\-[a-z0-9]+){0,}){0,})|()\/?$)/";
$uri = "www.domain.com/paramsindex/cont/meth/par1/par2/par3/";
$r1 = preg_match($reg1, $uri);
echo "<p>First regex returned: {$r1}</p>";
$r2 = preg_match($reg2, $uri);
echo "<p>Second regex returned: {$r2}</p>";
Now these strings are not the same, difference is this:
www.domain.com/paramsindex/cont/meth/par1/par2/par3/
vs.
www.domain.com/paramsassoc/cont/meth/par1/par2/par3/
And yet PHP preg_match returns 1 for both of them.
Now you will say this is a long regex and why use that. And the thing is I could built shorter regex but it is built on the fly and... it youst needs to be like that.
And what bothers me is that in Rubular regexs works as it should.
When testing them I was using Rubular, and now i PHP it wont work. I know Rubular is Ruby regex editor but I tought it should be the same :(
Rubular testing:here
What is problem here? How should I write that regex in PHP so preg_match can see the difference? And regex should be as close to the one I already wrote, is there some simple fix to my problem? Something im overlooking?

Answer 1

That behavior is by design, preg_match returns 1 when a match is found. If you want to capture matches, see the matches parameter at: http://php.net/manual/en/function.preg-match.php
Edit: For example
$matches = array();
$r2 = preg_match($reg2, $uri, $matches);
echo "<p>Second regex returned: ";
print_r($matches);
echo "</p>";
I'll leave the above to document my own stupidity for not answering the right question.
At the end of your regex you have |()\/?$)/ which will make the regex match URL that ends with a slash. Take it out and it looks like you're golden from my tests.

Answer 2

Always remember to group your operands!
I can assume that this one is can be quite hard to spot, but it's all because of your use of the or-operator |. You are not grouping the operands correctly and therefore the result described in your post is being yield.
Your use of |() in the provided case will match either nothing or the full regular expression to the left of your operator |.
To solve this issue you will need to put parentheses around the operands that should be ORed.
An easy method of seeing where everything goes wrong is to run this below snippet:
$reg1 = "/(^(((www\.))|(?!(www\.)))domain\.com\/paramsindex\/([a-z]+)\/([a-z]+)\/((([a-z0-9]+)(\-[a-z0-9]+){0,})(\/([a-z0-9]+)(\-[a-z0-9]+){0,}){0,})|()\/?$
$reg2 = "/(^(((www\.))|(?!(www\.)))domain\.com\/paramsassoc\/([a-z]+)\/([a-z]+)\/((([a-z0-9]+)(\-[a-z0-9]+){0,})(\/([a-z0-9]+)(\-[a-z0-9]+){0,}){0,})|()\/?$
$uri = "www.domain.com/paramsindex/cont/meth/par1/par2/par3/";
var_dump (preg_match($reg1, $uri, $match1));
var_dump (preg_match($reg2, $uri, $match2));
print_r ($match1);
print_r ($match2);
output
int(1)
int(1)
Array
(
[0] => www.domain.com/paramsindex/cont/meth/par1/par2/par3
[1] => www.domain.com/paramsindex/cont/meth/par1/par2/par3
[2] => www.
[3] => www.
[4] => www.
[5] =>
[6] => cont
[7] => meth
[8] => par1/par2/par3
[9] => par1
[10] => par1
[11] =>
[12] => /par3
[13] => par3
)
Array
(
[0] => /
[1] => /
[2] =>
[3] =>
[4] =>
[5] =>
[6] =>
[7] =>
[8] =>
[9] =>
[10] =>
[11] =>
[12] =>
[13] =>
[14] =>
[15] =>
)
As you see $reg2 matches a bunch of empty strings in $uri, which is an indication of what I described earlier.
If you come up with a short description of what you are trying to do I can provide you with a fully functional (and probably a bit neater than you current) regular expression.

Answer 3

Your RegEx is a mess and you will have to change it if you want it to work.
Check out the Rubular for your paramsindex: http://www.rubular.com/r/3ptjQ5aIrD
Now, for paramsassoc: http://www.rubular.com/r/o7GCbCsHyX
They both return a result. Sure it's an array full of empty strings, but it is a result nontheless.
That is why both are TRUE.