How to get POST array value in PHP
This article will introduce the basic usage of PHP’s post array to get a value from an input form. The article will also highlight some important points about how to use post arrays, what they are used for, and where you can find more information about them.
PHP provides an array data type for storing collections of values. The POST variable is a form input that gets sent to your PHP code by the web browser, and it allows you to store multiple values passed in from the HTML form.
An Introduction To POST Arrays in PHP.
A POST array stores data that was sent to the server by a form.
Both these methods place limitations on what can be sent to the server, GET requests are limited to 8-bit ASCII and browsers may prevent more than 2kb of data from being submitted in a single transaction.
POST arrays can store extremely large amounts of data without any limitations. Imagine you have an HTML form that asks people for their entire resume, in this case, it would make sense to save the data submitted by the form to a POST array.
How are POST arrays created?
Creating a new PHP post array is different than creating a normal array because you must tell PHP which special variable name it should use to store the post data.
There are many special variables that PHP uses, but we’re only concerned with $_POST . $_POST contains all values submitted via the HTTP POST method. $_REQUEST – Contains all values submitted via any method (GET, POST, COOKIE, etc).
As mentioned earlier GET requests can’t send very much data at once and as such, they shouldn’t be used for sending large amounts of information (like user uploads) or large forms (like user resumes).
How to get POST array value in PHP
To get all post data in PHP, we have to use the $_POST superglobal variable. You can retrieve the value of a specific key using $_POST[‘key’] syntax but if the key does not exist then this returns an empty string.
If you want to check that a given key exists or not, use the isset() function, for example:
If you want to know whether the given POST array has any content, use empty() function, for example:
Retrieve post array values
If you want to pass an array into a post variable you can do this like below-
Cooking
Singing
Playing
Swimming
We now want to see which hobby the user has selected.
http_build_query
Generates a URL-encoded query string from the associative (or indexed) array provided.
Parameters
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.
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.
The argument separator. If not set or null , arg_separator.output is used to separate arguments.
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
Examples
Example #1 Simple usage of http_build_query()
$data = array(
‘foo’ => ‘bar’ ,
‘baz’ => ‘boom’ ,
‘cow’ => ‘milk’ ,
‘null’ => null ,
‘php’ => ‘hypertext processor’
);
echo http_build_query ( $data ) . «\n» ;
echo http_build_query ( $data , » , ‘&’ );
The above example will output:
foo=bar&baz=boom&cow=milk&php=hypertext+processor foo=bar&baz=boom&cow=milk&php=hypertext+processor
Example #2 http_build_query() with numerically index elements.
$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
$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
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’ ;
>
echo http_build_query ( $parent );
?>
The above example will output:
pub=publicParent&pub_bar%5Bpub%5D=publicChild
See Also
- parse_str() — Parses the string into variables
- 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
User Contributed Notes 24 notes
Params with null value do not present in result string.
$arr = array( ‘test’ => null , ‘test2’ => 1 );
echo http_build_query ( $arr );
?>
will produce:
Number to string conversion occured in is affected by locale settings, which might not be obvious.
setlocale ( LC_ALL , ‘us_En’ );
http_build_query ( $params ) // v=5.63
setlocale ( LC_ALL , ‘ru_RU’ );
http_build_query ( $params ) // v=5,63 mind the comma
?>
Passing null to $arg_separator is the same as passing an empty string, which is probably not what you want.
If you need to change the enc_type, use this:
http_build_query($query, null, ini_get(‘arg_separator.output’), PHP_QUERY_RFC3986);
// BAD CODE!
http_build_query($query, null, null, PHP_QUERY_RFC3986);
if you send boolean values it transform in integer :
$a = [teste1= true,teste2=false];
echo http_build_query($a)
//result will be teste1=1&teste2=0
This function makes like this
$query = http_build_query($query);
$query = preg_replace(‘/%5B9+%5D/simU’, ‘%5B%5D’, $query);
As noted before, with php5.3 the separator is & on some servers it seems. Normally if posting to another php5.3 machine this will not be a problem.
But if you post to a tomcat java server or something else the & might not be handled properly.
http_build_query($array); //gives & to some servers
If you need the inverse functionality, and (like me) you cannot use pecl_http, you may want to use something akin to the following.
// mimic the behavior of $_GET, see also RFC 1738 and 3986.
$Delimiter = ini_get ( ‘arg_separator.input’ );
$Params = array();
if (!empty( $NameValueParts [ ‘indices_present’ ])) $Indices = explode ( ‘][‘ , $NameValueParts [ ‘indices’ ]);
foreach ( $Indices as $Index ) if (! is_array ( $Param )) $Param = array();
>
if ( $Index === » ) $Param [] = array();
end ( $Param );
$Param =& $Param [ key ( $Param )];
> else if ( ctype_digit ( $Index ))
if (! array_key_exists ( $Index , $Param )) $Param [ $Index ] = array();
>
$Param =& $Param [ $Index ];
>
>
>
if (!empty( $NameValueParts [ ‘value_present’ ])) $Param = urldecode ( $NameValueParts [ ‘value’ ]);
> else $Param = » ;
>
>
>
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);
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:
$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.
$ch = curl_init ( $some_url );
curl_setopt ( $ch , CURLOPT_POST , true );
curl_setopt ( $ch , CURLOPT_POSTFIELDS , $post_url );
curl_exec ( $ch );
?>
Note that at the final page that processes the POST data, you should be properly filtering/escaping it.
As noted, this function omits keys with null values. This could break some code which treats the key as boolean, and so has no value, or other code expecting the array to be populated regardless of value.
A workaround for this is to replace the null values with an empty string:
// Compensate for fact that http_build_query omits null values
foreach($data as &$datum) if($datum===null) $datum=»;
Losing the null-ness of the original is no real loss if it’s supposed to be a real query string. If the null is important, you could use a dummy value instead.
Be careful about Example 1 — it is exactly how *not* to implement things.
You should HTML encode your URL if embedding it in a web page. This is more involved than just replacing & with &. Doing as this example suggests is a security hole waiting to happen.
Correct implementation of coding the array of params without indexes (valdikks fixed code — didnt work for inner arrays):
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.
on my install of PHP 5.3, http_build_query() seems to use & as the default separator. Kind of interesting when combined with stream_context_create() for a POST request, and getting $_POST[‘amp;fieldName’] on the receiving end.
When using http_build_query($args) where $args is an array; note that there is a limit to the size of array. See max_input_vars in your php.ini to increase this size.