Generate URL-encoded query string

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- PHP Manual
- URL Functions
- Generate URL-encoded query string

# http_build_query

(PHP 5, PHP 7, PHP 8)

http_build_query — Generate URL-encoded query string

### Description

http_build_query(
array|object `$data`,
string `$numeric_prefix` = "",
?string `$arg_separator` = `null`,
int `$encoding_type` = `PHP_QUERY_RFC1738`
): string

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

### Parameters

`data`

  May be an array or object containing properties.

  If `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 `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`

  The argument separator. If not set or `null`, arg_separator.output is used to separate arguments.

`encoding_type`

  By default, `PHP_QUERY_RFC1738`.

  If `encoding_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 `encoding_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
--- | ---
8.0.0 | `arg_separator` is now nullable.

### Examples

Example #1 Simple usage of http_build_query()

    <?php
    $data = array(
        'foo' => 'bar',
        'baz' => 'boom',
        'cow' => 'milk',
        'null' => null,
        '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', null, '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&4=boom&cow=milk&php=hypertext+processor
    myvar_0=foo&myvar_1=bar&myvar_2=baz&myvar_4=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_');
    ?>

The above example 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

- parse_str() - Parse a string as a URL query string
- parse_url() - Parse a URL and return its components
- urlencode() - URL-encodes string
- array_walk() - Apply a user supplied function to every member of an array