How to pass an array within a query string

Question

Is there a standard way of passing an array through a query string    To be clear  I have a query string with multiple values  one of which would be an array value   I want that query string value to be treated as an array- I don t want the array to be exploded so that it is indistinguishable from the other query string variables   Also  according to this post answer  the author suggests that query string support for arrays is not defined   Is this accurate     EDIT   Based on  Alex s answer  there is no standard way of doing this  so my follow up is then what is an easy way to recognize that the paramater I m reading is an array in both PHP and Javascript     Would it be acceptable to name multiple params the same name  and that way I would know that they belong to an array  Example    myarray value1 amp myarray value2 amp myarray value3      Or would this be bad practice

User · Answer

A query string carries textual data so there is no option but to explode the array, encode it correctly and pass it in a representational format of your choice:

p1=value1&pN=valueN...
data=[value1,...,valueN]
data={p1:value1,...,pN:valueN}

and then decode it in your server side code.

User · Answer

I don t think there s a standard  Each web environment provides its own  standard  for such things  Besides  the url is usually too short for anything  256 bytes limit on some browsers   Of course longer arrays data can be send with POST requests   However  there are some methods    There s a PHP way  which uses square brackets       in URL queries  For example a query such as  array name   item amp array name   item 2 has been said to work  despite being poorly documented  with PHP automatically converting it into an array  Source  https   stackoverflow com a 9547490 3787376 Object data-interchange formats  e g  JSON - official website  PHP documentation  can also be used if they have methods of converting variables to and from strings as JSON does  Also an url-encoder  available for most programming languages  is required for HTTP get requests to encode the string data correctly    Although the  square brackets method  is simple and works  it is limited to PHP and arrays  If other types of variable such as classes or passing variables within query strings in a language other than PHP is required  the JSON method is recommended   Example in PHP of JSON method  method 2      myarray   array 2  46  34   dfg     serialized   json encode  myarray   data    myarray     rawurlencode  serialized      Send to page via cURL  header   or other service    Code for receiving page  PHP      myarray   json decode   GET  myarray        Or   POST  myarray   if a post request

User · Answer

Although there isn t a standard on the URL part  there is one standard for JavaScript  If you pass objects containing arrays to URLSearchParams  and call toString   on it  it will transform it into a comma separated list of items  let data       str   abc     arr    abc   123     new URLSearchParams data  toString        str abc amp arr abc 123  with escaped characters

User · Answer

Here s what I figured out   Submitting multi-value form fields  i e  submitting arrays through GET POST vars  can be done several different ways  as a standard is not necessarily spelled out   Three possible ways to send multi-value fields or arrays would be     cars   Saab amp cars   Audi  Best way- PHP reads this into an array   cars Saab amp cars Audi  Bad way- PHP will only register last value   cars Saab Audi  Haven t tried this    Form Examples  On a form  multi-valued fields could take the form of a select box set to multiple    lt form gt        lt select multiple  multiple  name  cars    gt            lt option gt Volvo lt  option gt            lt option gt Saab lt  option gt            lt option gt Mercedes lt  option gt        lt  select gt   lt  form gt     NOTE  In this case  it would be important to name the select control some name    so that the resulting request vars would be registered as an array by PHP         or as multiple hidden fields with the same name    lt input type  hidden  name  cars    value  Volvo  gt   lt input type  hidden  name  cars    value  Saab  gt   lt input type  hidden  name  cars    value  Mercedes  gt      NOTE  Using field   for multiple values is really poorly documented  I don t see any mention of it in the section on multi-valued keys in Query string - Wikipedia  or in the W3C docs dealing with multi-select inputs     UPDATE  As commenters have pointed out  this is very much framework-specific  Some examples   Query string    list a 1 amp list a 2 amp list a 3 amp list b   1 amp list b   2 amp list b   3 amp list c 1 2 3   Rails    list a    3     list b         1        2        3         list c    1 2 3    Angular     list a          1        2        3          list b            1        2        3          list c    1 2 3     Angular discussion   See comments for examples in node js  Wordpress  ASP net    Maintaining order  One more thing to consider is that if you need to maintain the order of your items  i e  array as an ordered list   you really only have one option  which is passing a delimited list of values  and explicitly converting it to an array yourself

User · Answer

I use React and Rails  I did   js    let params         filter array    A    B    C                   transform params in URI    Object keys params  map key   gt        if  Array isArray params key            return params key  map  value    gt     key      value    join   amp                  filter array   A amp filter array   B amp filter array   C

User · Answer

Check the parse string function http   php net manual en function parse-str php  It will return all the variables from a query string  including arrays   Example from php net    lt  php  str      first value amp arr   foo bar amp arr   baz   parse str  str   echo   first         value echo   arr 0        foo  bar echo   arr 1        baz  parse str  str    output   echo   output  first           value echo   output  arr   0        foo  bar echo   output  arr   1        baz    gt

User · Answer

I feel it would be helpful for someone who is looking for passing the array in a query string to a servlet  I tested below query string and was able to get the array values using req getgetParameterValues    method  Below is the query string I passed through browser     http   localhost 8080 ServletsTutorials   html     myname abc amp initial xyz amp checkbox a amp checkbox b   checkbox is my parameter array here

User · Answer

You mention PHP and Javascript in your question  but not in the tags  I reached this question with the intention of passing an array to an MVC Net action   I found the answer to my question here  the expected format is the one you proposed in your question  with multiple parameters having the same name

User · Answer

This works for me   In link  to attribute has value   to   filter arr fruits apple amp fruits banana    Route can handle this   path   filter  arr    For Multiple arrays   to  filter arr fruits apple amp fruits banana amp vegetables potato amp vegetables onion    Route stays same   SCREENSHOT

User · Answer

You can use http build query to generate a URL-encoded querystring from an array in PHP  Whilst the resulting querystring will be expanded  you can decide on a unique separator you want as a parameter to the http build query method  so when it comes to decoding  you can check what separator was used  If it was the unique one you chose  then that would be the array querystring otherwise it would be the normal querystrings

[php] How to pass an array within a query string?

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