REGEX: Extract parameter from URL

Question

What REGEX should I use to extract the following parameter from a url string:

/?c=135&a=1341

I basically want to get the value of the a parameter from this string.

Thanks,

There are two parameters in this url. Which one do you want? — bmargulies
– bmargulies, Commented Feb 12, 2012 at 16:53
As pointed out in my question, I am looking to extract the a value. I have already solved it.. see answer form bunting — AKKAweb
– AKKAweb, Commented Feb 12, 2012 at 22:46

AKKAweb · Accepted Answer · 2012-02-12 18:16:54Z

1

If you want to extract the value of a, and the value consists of one to many digits, this regex should work:

preg_match("/a=(\\d{1,})/ui", $_SERVER['REQUEST_URI'], $matches)

Then use $matches[1] to display the a value

edited Feb 12, 2012 at 18:16

AKKAweb

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answered Feb 12, 2012 at 16:55

Kai Sternad

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3 Comments

AKKAweb Over a year ago

I wasnt able to get this working but I was able to find the following solution: preg_match("/\?c=(\w+)\&a=(\w+)/i", $_SERVER['REQUEST_URI'], $matches); Thanks for helping...

Kai Sternad Over a year ago

Sure, with PHP the above would be: preg_match("/a=(\\d{1,})/ui", $searchText)

AKKAweb Over a year ago

PERFECT. This works. Yeah, I should have pointed that out before that I was using PHP. Everything works good now... t

TerryE · Accepted Answer · 2012-02-12 17:35:01Z

1

I am going to answer a slightly more general Q which is suggested by your ? prefix that you are trying to remove a specific parameter from a URI request string (which drops the leading ?). And in this case using the mod_rewrite engine so that you can implement this in your .htaccess file.

The rule is somewhat more complex because you don't necessarily know where in the query parameters a=XXX comes, so you need different regexps for the case where a is first and a is a subsequent parameter. You do this by ((?=a=)regexp1|regexp2) so here it is:

 RewriteEngine on
 RewriteBase   \
 RewriteCond   %{QUERY_STRING} ^(?(?=a=)a=[^&]*&?(.*)|(.*)&a=[^&]*(&.*)?)
 RewriteRule   ^.*             $0?%1%2%3                        [L]

If a is first the %1 contain rest otherwise %2 and %3 the bookends (%3 may be blank).

If you want this to occur for specific scripts then replace the rule regexp ^.* by a more specific one.

Enjoy :-)

answered Feb 12, 2012 at 17:35

TerryE

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5 Comments

TerryE Over a year ago

The same regexp will work in a preg_match() but why aren't you just using $_GET ???

AKKAweb Over a year ago

I tried the stay away from .htaccess. I tried that before but did not work... maybe something is wrong with my system. I will check...

TerryE Over a year ago

I note that you still ducked my Q as to why to are editing $_SERVER['REQUEST_URI'] and not just using $_GET :-)

AKKAweb Over a year ago

I am not sure how to use _GET in this situation. Can you suggest something for my learning. Thanks

TerryE Over a year ago

Sure if you want to ignore a variable then just don't use it or unset it -- or are you calling some 3rd-part framework that accesses $_SERVER['REQUEST_URI']

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