regular expression parse url parameter

Question

I'm having trouble retrieving a URL parameter from a string using regular expressions:

An example string could be

some text and http://google.com/?something=this&tag=yahoo.com and more text, and I would like to be able to find yahoo.com from this.

The caveat is that I need to ensure that the string begins with http://google.com, and not just search for &tag=(.*)

preg_match("/google\.com\/.*&tag=(.*) $/", $subject, $matches)

i'm hoping this matches anything with google.com followed by anything, followed by &tag= followed by a space. Ultimately the goal is to parse out all of the tag= values from google.com URLs.

Is there a better way to accomplish this?

Update:

so I have this new regex: /google\.com\/.*(tag=.*)/ but i'm not sure how to get it to end on a space after the URL

I'm hoping to match the end of the string with a space... (i should probably add $) — d-_-b
– d-_-b, Commented Aug 7, 2013 at 22:27
Do not hope. Create lit of URLs that you want to pass, other list of invalid ones and write unit test to check if your function does what you want it to. — dev-null-dweller
– dev-null-dweller, Commented Aug 7, 2013 at 22:31

castis · Accepted Answer · 2013-08-08 06:01:02Z

4

get friendly with the parse_url() function!

$pieces = parse_url('some text http://google.com/?something=this&tag=yahoo.com and whatever');
$query = explode('&', $pieces['query']);

parse_str($pieces['query'], $get);
array_walk($get, function(&$item){
    if (!$sp = strpos($item, ' ')) return;
    $item = substr($item, 0, $sp);
});

var_dump($get); // woo!

edit: thanks to Johnathan for the parse_str() function.

edited Aug 8, 2013 at 6:01

answered Aug 7, 2013 at 22:28

castis

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3 Comments

d-_-b Over a year ago

thanks, never used that - but the string in this example will be more text than just the URL

Jonathan Kuhn Over a year ago

Don't forget parse_str to parse the query string.

castis Over a year ago

@d-_-b, theres no problem that theres extra text, parse_url pulls it out.

HamZa · Accepted Answer · 2013-08-07 22:38:05Z

1

If you want to get the value of tag then the following regex will do the job:

$string = 'some text and http://google.com/?something=this&tag=yahoo.com
and more text
http://google.com/?something=this&tag=yahoo2.com&param=test
';
preg_match_all('#http://google.com\S+&tag=([^\s&]+)#', $string, $m);
print_r($m[1]);

Output

Array
(
    [0] => yahoo.com
    [1] => yahoo2.com
)

Explanation

http://google.com : match http://google.com
\S+ : match non whitespace one or more times
&tag= : match &tag=
([^\s&]+) : match anything except whitespace and & one or more times and group it

If you want, you may even add s? after http to take in account for https, or add the i modifier to match case insensitive.

answered Aug 7, 2013 at 22:38

HamZa

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2 Comments

d-_-b Over a year ago

this is great! thanks! I'll review this in a little while... quick question, why the # at the start?

HamZa Over a year ago

@d-_-b It's the modifier. I used # instead of / which you're using. Why ? Because if I use a different modifier than / then I wouldn't need to escape those slashes for example in http:// :)

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