PHP http_build_query() Function

The PHP http_build_query() function generates a URL-encoded query string from the associative (or indexed) array provided.

Syntax

http_build_query(data, numeric_prefix, 
                 arg_separator, encoding_type)

Parameters

`data`	`Required.` Specify data. It may be an array or object containing properties. If data is an array, it can be a single dimensional array or multi-dimensional array. If data is an object, then only public properties will be incorporated into the result.
`numeric_prefix`	`Optional.` 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.
`arg_separator`	`Optional.` arg_separator.output is used to separate arguments but may be overridden by specifying this parameter. arg_separator.output can be set in php.ini.
`encoding_type`	`Optional.` Specify the encoding type. Default is PHP_QUERY_RFC1738. It can take the following values: PHP_QUERY_RFC1738 : encoding is performed according to RFC 1738 and the application/x-www-form-urlencoded media type, which implies that spaces are encoded as plus (+) signs. PHP_QUERY_RFC3986 : encoding is performed according to RFC 3986, and spaces will be percent encoded (%20).

Return Value

Returns a URL-encoded string.

Example: http_build_query() example

The example below shows the simple usage of http_build_query() function.

<?php
$info = array(
  'lang' => 'php',
  'topic' => 'function-reference',
  'example' => '1',
  'null' => null,
  'php' => 'hypertext processor'
);

echo http_build_query($info)."\n";

//using # as argument separator
echo http_build_query($info, '', '#');
?>

The output of the above code will be:

lang=php&topic=function-reference&example=1&php=hypertext+processor
lang=php#topic=function-reference#example=1#php=hypertext+processor

Example: using numeric index array

The example below shows the usage of numeric_prefix parameter.

<?php
$info = array('php', 'function-reference', 
              '1', null, 'hypertext processor');

echo http_build_query($info)."\n";

//using 'myvar_' as numeric_prefix parameter 
//to prepend it to the numeric index
echo http_build_query($info, 'myvar_');
?>

The output of the above code will be:

0=php&1=function-reference&2=1&4=hypertext+processor
myvar_0=php&myvar_1=function-reference&myvar_2=1&myvar_4=hypertext+processor

Example: using multi-dimensional array

A multi-dimensional array can also be used with this function as shown in the example below:

<?php
$info = array(
  'Mike', 
  'age' => 55,
  'children' => array(
    'John' => array('age'=>12, 'gender'=>'M'),
    'Marry' => array('age'=>8, 'gender'=>'F')
));

echo http_build_query($info, 'var_');
?>

The output of the above code will be (word wrapped for readability):

var_0=Mike&age=55&children%5BJohn%5D%5Bage%5D=12&
children%5BJohn%5D%5Bgender%5D=M&children%5BMarry%5D
%5Bage%5D=8&children%5BMarry%5D%5Bgender%5D=F

Example: using an object

If an object is used, then only public properties is incorporated into the result. Consider the example below:

<?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 output of the above code will be:

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

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