regular expression to extract a query string parameter value from a URL in PHP

Question

I need to extract an item id from a URL; the pattern is this &R=10031004&, I mean, I need to extract the string within &R= and the other &

This is what I have so far, but I keep getting errors.

preg_match('^[&R=]+ &$',
"http://www.lapdirecciondemario.com/items.php&R=10031004&", $matches);
$host = $matches[0];

echo $host;

Your pattern is missing the delimiters - it's an invalid pattern. — Marc B
– Marc B, Commented Oct 24, 2011 at 18:09

middus · Accepted Answer · 2011-10-24 18:20:54Z

2

$url = 'http://www.lapdirecciondemario.com/items.php&R=10031004&';
preg_match('/(&|\?)R=([0-9]+)/i', $url, $matches);
echo $matches[2];

In contrast to the other answers, this will also match if the parameter R is preceded by a ? instead of a &. If you know more about the length of the number, you can replace the + after [0-9] with {min,max}.

This regular expression should be pretty robust and match all of these:

edited Oct 24, 2011 at 18:20

answered Oct 24, 2011 at 18:13

middus

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Comments

Aurelio De Rosa · Accepted Answer · 2011-10-24 18:08:16Z

1

Use this:

preg_match('/&R\=(.*?)&/i', "http://www.lapdirecciondemario.com/items.php&R=10031004&", $matches);
echo $matches[1]; // will echo 10031004

answered Oct 24, 2011 at 18:08

Aurelio De Rosa

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2 Comments

Aurelio De Rosa Over a year ago

@middus I answered the OP's question that ask to get the string between &R= and &, so there was no need to do a regex for other strings.

middus Over a year ago

Yeah, I know. But the URL given by the OP is likely to be invalid.

Dejan Marjanović · Accepted Answer · 2011-10-24 18:07:50Z

0

preg_match('#R=([0-9]+)#is', "http://www.lapdirecciondemario.com/items.php&R=10031004&", $matches);
echo $matches[1]; # 10031004

answered Oct 24, 2011 at 18:07

Dejan Marjanović

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1 Comment

Dejan Marjanović Over a year ago

@middus, it can be pretty much anything as long as Delimiter must not be alphanumeric or backslash is satisfied. Try ~ or even * for example.

sharpner · Accepted Answer · 2011-10-24 18:07:58Z

0

well first of all maybe I can simplify your task,

is this the url from the script?

then you should check the contents of $_GET where you will find a variable R with contents 10031004...

$item_id = $_GET['R']; 
echo $item_id;

answered Oct 24, 2011 at 18:07

sharpner

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Dejan Marjanović Over a year ago

I think he is scraping website :)

FailedDev · Accepted Answer · 2011-10-24 18:09:37Z

0

if (preg_match('/(?<=&R=).*?(?=&)/', "http://www.lapdirecciondemario.com/items.php&R=10031004&", $regs)) {
    $result = $regs[0];
}

Use this one.

answered Oct 24, 2011 at 18:09

FailedDev

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2 Comments

Dejan Marjanović Over a year ago

why making simple things look complicated? :)

FailedDev Over a year ago

:) Why capture something not needed? :)

user8710 · Accepted Answer · 2011-10-24 18:22:24Z

0

I might as well chuck another at you. This one will match any character between an R= preceeded by ? or & and ending with & or #.

preg_match('/[?&]R=([^&#]+)/', "http://www.lapdirecciondemario.com/items.php&R=10031004&", $matches);

answered Oct 24, 2011 at 18:22

user8710

5 Comments

middus Over a year ago

If the id is supposed to be numeric, this does not add value.

user8710 Over a year ago

Yes, but his question says that he has to 'extract the string within &R= and the other &', so my answer is more precise.

middus Over a year ago

Your answer would match http://www.lapdirecciondemario.com/items.php&R=1003/IamtheWalrus/1004&, which is probably not what he wants or is it?

user8710 Over a year ago

Your regex returns 1003. Mine returns '1003/IamtheWalrus/1004'. Mine is more correct, based on the wording of the question. On the other hand, that input is absurd and neither is likely to be useful to lapdirecciondemario.com's meaning of R.

middus Over a year ago

There is no "more correct", just correct and not correct. If we assume the id to be numeric, this URL should not match. If we knew more about the id, we could specify {min,max} (see my answer) to further avoid false positives.

Saxoier · Accepted Answer · 2011-10-24 18:41:22Z

0

$url = "http://www.lapdirecciondemario.com/items.php&R=10031004&";
$urlQueryParts = array();
parse_str(parse_url($url, PHP_URL_QUERY), $urlQueryParts);
if(isset($urlQueryParts[ "R" ]))
    $urlQueryParts[ "R" ];

I couldn't test it but it should work.

answered Oct 24, 2011 at 18:41

Saxoier

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