How to get multiple parameters with same name from a URL in PHP

Question

I have a PHP application that will on occasion have to handle URLs where more than one parameter in the URL will have the same name. Is there an easy way to retrieve all the values for a given key? PHP $_GET returns only the last value.

To make this concrete, my application is an OpenURL resolver, and may get URL parameters like this:

ctx_ver=Z39.88-2004
&rft_id=info:oclcnum/1903126
&rft_id=http://www.biodiversitylibrary.org/bibliography/4323
&rft_val_fmt=info:ofi/fmt:kev:mtx:book
&rft.genre=book
&rft.btitle=At last: a Christmas in the West Indies. 
&rft.place=London,
&rft.pub=Macmillan and co.,
&rft.aufirst=Charles
&rft.aulast=Kingsley
&rft.au=Kingsley, Charles,
&rft.pages=1-352
&rft.tpages=352
&rft.date=1871

(Yes, I know it's ugly, welcome to my world). Note that the key "rft_id" appears twice:

rft_id=info:oclcnum/1903126
rft_id=http://www.biodiversitylibrary.org/bibliography/4323

$_GET will return just http://www.biodiversitylibrary.org/bibliography/4323, the earlier value (info:oclcnum/1903126) having been overwritten.

I'd like to get access to both values. Is this possible in PHP? If not, any thoughts on how to handle this problem?

For GET requests you can parse $_SERVER['QUERY_STRING'] yourself and for non-enctype="multipart/form-data" POST requests you can parse file_get_contents("php://input"). For POST requests with enctype="multipart/form-data" the submitted data needs to be modified to include [] at the end of the parameter name or the data is lost always. PHP cannot handle that case due brain damaged API to the data! — Mikko Rantalainen
– Mikko Rantalainen, Commented Nov 25, 2020 at 11:47

Tomalak · Accepted Answer · 2019-06-19 14:48:12Z

80

Something like:

$query  = explode('&', $_SERVER['QUERY_STRING']);
$params = array();

foreach( $query as $param )
{
  // prevent notice on explode() if $param has no '='
  if (strpos($param, '=') === false) $param += '=';

  list($name, $value) = explode('=', $param, 2);
  $params[urldecode($name)][] = urldecode($value);
}

gives you:

array(
  'ctx_ver'     => array('Z39.88-2004'),
  'rft_id'      => array('info:oclcnum/1903126', 'http://www.biodiversitylibrary.org/bibliography/4323'),
  'rft_val_fmt' => array('info:ofi/fmt:kev:mtx:book'),
  'rft.genre'   => array('book'),
  'rft.btitle'  => array('At last: a Christmas in the West Indies.'),
  'rft.place'   => array('London'),
  'rft.pub'     => array('Macmillan and co.'),
  'rft.aufirst' => array('Charles'),
  'rft.aulast'  => array('Kingsley'),
  'rft.au'      => array('Kingsley, Charles'),
  'rft.pages'   => array('1-352'),
  'rft.tpages'  => array('352'),
  'rft.date'    => array('1871')
)

Since it's always possible that one URL parameter is repeated, it's better to always have arrays, instead of only for those parameters where you anticipate them.

edited Jun 19, 2019 at 14:48

answered Dec 9, 2008 at 16:46

Tomalak

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9 Comments

Sam Over a year ago

if (!array_key_exists($name, $params)) $params[$name] = array(); Is unnecessary, $params[$name][] = $value will instantiate the array if it doesn't exist.

Mikko Rantalainen Over a year ago

Is there any way to get all parameter values with identical names in case of POST with file upload?

Tomalak Over a year ago

@Mikko: What do you mean by "identical names", exactly?

Mikko Rantalainen Over a year ago

@Tomalak: sorry, I've missed your response. I mean situation equivalent to GET /foo/bar?id=1&id=2&id=42&file=xyz. The $_SERVER["QUERY_STRING"] is usable for GET, file_get_contents("php://input") works for POST unless enctype="multipart/form-data" is used for the HTML form. How I can get list of id = array(1,2,42) if I cannot change to origin form and it's using enctype="multipart/form-data"?

Yaron U. Over a year ago

list($name, $value) = explode('=', $param, 2); will have a notice for query param without = sign (e.g. param1=1&params=&param3&param4=4). you should first check strpos($param, '=') !== false

|

benlumley · Accepted Answer · 2008-12-09 16:41:02Z

47

Won't work for you as it looks like you don't control the querystring, but another valid answer: Instead of parse querystring, you could appeand '[]' to the end of the name, then PHP will make an array of the items.

IE:

someurl.php?name[]=aaa&name[]=bbb

will give you a $_GET looking like:

array(0=>'aaa', 1=>'bbb')

answered Dec 9, 2008 at 16:41

benlumley

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2 Comments

Neil Aitken Over a year ago

Good suggestion, I wouldnt have thought of that I assumed that the OP didn't have access to change the values

Andrew Over a year ago

Note that you can also use numbers (or even strings) in the brackets to pass an associative array. So if you don't control it, don't rely on it being 0-indexed. someurl.php?name[5]=aaa&name[zip]=bbb

Community · Accepted Answer · 2017-05-23 12:10:36Z

I think you'd have to parse $_SERVER['QUERY_STRING'] manually.

Something like (untested):

$query = $_SERVER['QUERY_STRING'];
$vars = array();
foreach (explode('&', $query) as $pair) {
    list($key, $value) = explode('=', $pair);
    $vars[] = array(urldecode($key), urldecode($value));
}

This should give you an array $vars:

array(
    array('ctx_ver'     => 'Z39.88-2004'),
    array('rft_id'      => 'info:oclcnum/1903126'),
    array('rft_id'      => 'http://www.biodiversitylibrary.org/bibliography/4323'),
    array('rft_val_fmt' => 'info:ofi/fmt:kev:mtx:book'),
    array('rft.genre'   => 'book'),
    array('rft.btitle'  => 'At last: a Christmas in the West Indies.'),
    array('rft.place'   => 'London'),
    array('rft.pub'     => 'Macmillan and co.'),
    array('rft.aufirst' => 'Charles'),
    array('rft.aulast'  => 'Kingsley'),
    array('rft.au'      => 'Kingsley, Charles'),
    array('rft.pages'   => '1-352'),
    array('rft.tpages'  => '352'),
    array('rft.date'    => '1871')
)

After having seen Tomalak's answer, I like his data format for the resulting array much better, as it makes it possible to access specific keys by their name.

There's a missing ";" after the second line $vars = array(); and I need to wrap $_SERVER['QUERY_STRING'] in html_entity_decode to convert & to &, but once done works a treat. Many thanks.

Undo · Accepted Answer · 2020-05-08 22:23:38Z

10

There's no need to use explode workarounds for this. A simple regex can more easily rectify a QUERY_STRING with multiple like-named parameters:

// Replace `&x=1&x=2` into `x[]=1&x[]=2`
$qs = preg_replace("/(?<=^|&)(\w+)(?==)/", "$1[]", $_SERVER["QUERY_STRING"]);

Then it's as simple as using parse_str:

parse_str($qs, $new_GET);

Which has the advantage of correctly decoding %xy URL escapes right away.

If you just want a single or a few specific parameters extracted as array, then use (id|name) instead of (\w+) in the regex.

edited May 8, 2020 at 22:23

Undo♦

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answered Sep 21, 2015 at 17:34

mario

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Comments

Filip Roséen · Accepted Answer · 2012-07-05 03:34:37Z

Assumed you have a query string like this:

param1=2549&appname=appName1&appname=appName2&appname=appName3&appname=appName4&appname=appName5&apptype=thetype&idsess=1231324567980147dzeze55sd4&action=myaction

You can do this :

public static function getMultipleParameters()
    {
        $query = $_SERVER['QUERY_STRING'];
        $vars = array();
        $second = array();
        foreach (explode('&', $query) as $pair) {
            list($key, $value) = explode('=', $pair);
            if('' == trim($value)){
                continue;
            }

            if (array_key_exists($key, $vars)) {
                if (!array_key_exists($key, $second))
                    $second[$key][] .= $vars[$key];
                $second[$key][] = $value;
            } else {
                $vars[$key] = urldecode($value);
            }
        }
        return array_merge($vars, $second);
    }

That gives :

array (
  'param1' => '2549',
  'appname' => 
      array (
        0 => 'appName1',
        1 => 'appName2',
        2 => 'appName3',
        3 => 'appName4',
        4 => 'appName5',
  ),
  'apptype' => 'thetype',
  'idsess' => '1231324567980147dzeze55sd4',
  'action' => 'myaction',
);

Hope that helps ;)

Jin Kwon · Accepted Answer · 2017-05-08 02:20:29Z

2

AFAIK there is no way to get duplicate values using $_GET as the second value will overwrite the first

To get around it you could access the raw querystring using $_SERVER['QUERY_STRING'] and then parse it yourself.

edited May 8, 2017 at 2:20

Jin Kwon

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answered Dec 9, 2008 at 16:38

Neil Aitken

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Comments

Timo Huovinen · Accepted Answer · 2018-12-27 13:07:03Z

Sharing my version of this function

function parse_mstr($query_string,&$query=array()){
    $query = $query? $query: array();
    $params  = explode('&', $query_string);
    foreach( $params as $param ){
        $k = $param;
        $v = '';
        if(strpos($param,'=')){
            list($name, $value) = explode('=', $param);
            $k = rawurldecode($name);
            $v = rawurldecode($value);
        }
        if(array_key_exists($k, $query)){
            if(is_array($query[$k])){
                $query[$k][] = $v;
            }else{
                $query[$k] = array($query[$k],$v);
            }
        }else{
            $query[$k] = $v;
        }
    }
}

// usage
parse_mstr('a=1&a=2&b=3', $arr);

// resulting array
$arr = [
    'a' => ['1', '2'],
    'b' => '3'
]

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