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http_build_query

(PHP 5)

http_build_queryGenerate URL-encoded query string

Description

string http_build_query ( mixed $query_data [, string $numeric_prefix [, string $arg_separator [, int $enc_type = PHP_QUERY_RFC1738 ]]] )

Generates a URL-encoded query string from the associative (or indexed) array provided.

Parameters

query_data

May be an array or object containing properties.

If query_data is an array, it may be a simple one-dimensional structure, or an array of arrays (which in turn may contain other arrays).

If query_data is an object, then only public properties will be incorporated into the result.

numeric_prefix

If numeric indices are used in the base array and this parameter is provided, it will be prepended to the numeric index for elements in the base array only.

This is meant to allow for legal variable names when the data is decoded by PHP or another CGI application later on.

arg_separator

arg_separator.output is used to separate arguments, unless this parameter is specified, and is then used.

enc_type

By default, PHP_QUERY_RFC1738.

If enc_type is PHP_QUERY_RFC1738, then encoding is performed per » RFC 1738 and the application/x-www-form-urlencoded media type, which implies that spaces are encoded as plus (+) signs.

If enc_type is PHP_QUERY_RFC3986, then encoding is performed according to » RFC 3986, and spaces will be percent encoded (%20).

Return Values

Returns a URL-encoded string.

Changelog

Version Description
5.4.0 The enc_type parameter was added.
5.1.3 Square brackets are escaped.
5.1.2 The arg_separator parameter was added.

Examples

Example #1 Simple usage of http_build_query()

<?php
$data 
= array('foo'=>'bar',
              
'baz'=>'boom',
              
'cow'=>'milk',
              
'php'=>'hypertext processor');

echo 
http_build_query($data) . "\n";
echo 
http_build_query($data'''&amp;');

?>

The above example will output:

foo=bar&baz=boom&cow=milk&php=hypertext+processor
foo=bar&amp;baz=boom&amp;cow=milk&amp;php=hypertext+processor

Example #2 http_build_query() with numerically index elements.

<?php
$data 
= array('foo''bar''baz''boom''cow' => 'milk''php' =>'hypertext processor');

echo 
http_build_query($data) . "\n";
echo 
http_build_query($data'myvar_');
?>

The above example will output:

0=foo&1=bar&2=baz&3=boom&cow=milk&php=hypertext+processor
myvar_0=foo&myvar_1=bar&myvar_2=baz&myvar_3=boom&cow=milk&php=hypertext+processor

Example #3 http_build_query() with complex arrays

<?php
$data 
= array('user'=>array('name'=>'Bob Smith',
                            
'age'=>47,
                            
'sex'=>'M',
                            
'dob'=>'5/12/1956'),
              
'pastimes'=>array('golf''opera''poker''rap'),
              
'children'=>array('bobby'=>array('age'=>12,
                                               
'sex'=>'M'),
                                
'sally'=>array('age'=>8,
                                               
'sex'=>'F')),
              
'CEO');

echo 
http_build_query($data'flags_');
?>

this will output : (word wrapped for readability)

user%5Bname%5D=Bob+Smith&user%5Bage%5D=47&user%5Bsex%5D=M&
user%5Bdob%5D=5%2F12%2F1956&pastimes%5B0%5D=golf&pastimes%5B1%5D=opera&
pastimes%5B2%5D=poker&pastimes%5B3%5D=rap&children%5Bbobby%5D%5Bage%5D=12&
children%5Bbobby%5D%5Bsex%5D=M&children%5Bsally%5D%5Bage%5D=8&
children%5Bsally%5D%5Bsex%5D=F&flags_0=CEO

Note:

Only the numerically indexed element in the base array "CEO" received a prefix. The other numeric indices, found under pastimes, do not require a string prefix to be legal variable names.

Example #4 Using http_build_query() with an object

<?php
class parentClass {
    public    
$pub      'publicParent';
    protected 
$prot     'protectedParent';
    private   
$priv     'privateParent';
    public    
$pub_bar  Null;
    protected 
$prot_bar Null;
    private   
$priv_bar Null;

    public function 
__construct(){
        
$this->pub_bar  = new childClass();
        
$this->prot_bar = new childClass();
        
$this->priv_bar = new childClass();
    }
}

class 
childClass {
    public    
$pub  'publicChild';
    protected 
$prot 'protectedChild';
    private   
$priv 'privateChild';
}

$parent = new parentClass();

echo 
http_build_query($parent);
?>

The above example will output:

pub=publicParent&pub_bar%5Bpub%5D=publicChild

See Also

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User Contributed Notes 12 notes

up
22
Ilya Rudenko
8 years ago
Params with null value do not present in result string.

<?
$arr
= array('test' => null, 'test2' => 1);
echo
http_build_query($arr);
?>

will produce:

test2=1
up
8
eric dot muyser at gmail dot com
1 year ago
This function makes like this

files[0]=1&files[1]=2&...

To do it like this:

files[]=1&files[]=2&...

Do this:

        $query = http_build_query($query);
        $query = preg_replace('/%5B[0-9]+%5D/simU', '%5B%5D', $query);
up
3
Vitaly Dyatlov
1 year ago
Correct implementation of coding the array of params without indexes (valdikks fixed code - didnt work for inner arrays):

<code>
function cr_post($a,$b='',$c=0)
        {
            if (!is_array($a)) return false;
            foreach ((array)$a as $k=>$v)
            {
                if ($c)
                {
                    if( is_numeric($k) )
                        $k=$b."[]";
                    else
                        $k=$b."[$k]";
                }
                else
                {   if (is_int($k))
                        $k=$b.$k;
                }

                if (is_array($v)||is_object($v))
                {
                    $r[]=cr_post($v,$k,1);
                        continue;
                }
                $r[]=urlencode($k)."=".urlencode($v);
            }
            return implode("&",$r);
        }
</code>
up
3
netrox at aol dot com
5 years ago
I noticed that even with the magic quotes disabled, http_build_query() automagically adds slashes to strings.

So, I had to add "stripslashes" to every string variable.
up
4
irish [-@-] ytdj [-dot-] ca
4 years ago
When using the http_build_query function to create a URL query from an array for use in something like curl_setopt($ch, CURLOPT_POSTFIELDS, $post_url), be careful about the url encoding.

In my case, I simply wanted to pass on the received $_POST data to a CURL's POST data, which requires it to be in the URL format.  If something like a space [ ] goes into the http_build_query, it comes out as a +. If you're then sending this off for POST again, you won't get the expected result.  This is good for GET but not POST.

Instead you can make your own simple function if you simply want to pass along the data:

<?php
$post_url
= '';
foreach (
$_POST AS $key=>$value)
   
$post_url .= $key.'='.$value.'&';
$post_url = rtrim($post_url, '&');
?>

You can then use this to pass along POST data in CURL.

<?php
    $ch
= curl_init($some_url);
   
curl_setopt($ch, CURLOPT_POST, true);
   
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_url);
   
curl_exec($ch);
?>

Note that at the final page that processes the POST data, you should be properly filtering/escaping it.
up
5
anonymous
2 years ago
Is it worth noting that if query_data is an associative array and a value is itself an empty array, or an array of nothing but empty array (or arrays containing only empty arrays etc.), the corresponding key will not appear in the resulting query string?
E.g.

$post_data = array('name'=>'miller', 'address'=>array('address_lines'=>array()), 'age'=>23);
echo http_build_query($post_data);

will print
name=miller&age=23
up
2
v0idnull[try_to_spam_me_now] at gee-mail dot co
4 years ago
on my install of PHP 5.3, http_build_query() seems to use &amp; as the default separator. Kind of interesting when combined with stream_context_create() for a POST request, and getting $_POST['amp;fieldName'] on the receiving end.
up
4
Anonymous
3 years ago
As noted before, with php5.3 the separator is &amp; on some servers it seems. Normally if posting to another php5.3 machine this will not be a problem.

But if you post to a tomcat java server or something else the &amp; might not be handled properly.

To overcome this specify:

http_build_query($array, '', '&');

and NOT

http_build_query($array); //gives &amp; to some servers
up
3
valdikss at gmail dot com
7 years ago
This function is wrong for http!
arrays in http is like this:

files[]=1&files[]=2&...

but function makes like this

files[0]=1&files[1]=2&...

Here is normal function:

<?php
function cr_post($a,$b=\'\',$c=0){
if (!is_array($a)) return false;
foreach ((array)$a as $k=>$v){
if ($c) $k=$b.\"[]\"; elseif (is_int($k)) $k=$b.$k;
if (is_array($v)||is_object($v)) {$r[]=cr_post($v,$k,1);continue;}
$r[]=urlencode($k).\"=\".urlencode($v);}return implode(\"&\",$r);}
?>
up
1
stocki dot r at gmail dot com
1 year ago
If you need only key+value pairs, you can use this:

<?php
    $array
= array(
       
"type" => "welcome",
       
"message" => "Hello World!"
   
);
    echo
urldecode(http_build_query($array, '', ';'));
?>

Result: type=welcome;message=Hello World!
up
0
Kirils Solovjovs
1 year ago
instead of some other suggestions that did not work for me, I found that the best way to build POST content (e.g. for stream_context_create) is urldecode(http_build_query($query))
up
-9
jakub dot lopuszanski at nasza-klasa dot pl
9 months ago
While this is not documented, this http_build_query can return FALSE on some inputs:
<?php
 
//gives bool(false)
 
var_dump(http_build_query('whatever'));
?>
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