json code integrated with php - php

Question

I have these following code. could anyone please explain it to me about these code, I did not get all of them.
here is the code
$query = $_SERVER['QUERY_STRING'];
$query = explode('&', $_SERVER['QUERY_STRING']);enter code here
$params = array();
foreach ($query as $param) {
list($name, $value) = explode('=', $param, 2);
$params[urldecode($name)][] = urldecode($value);
}
//echo jsonEncode($params);
$categories = implode(", ", $params['categories']);
$types = implode(", ", $params['type']);
I am confused about these two variables "$param" & "$params"

Answer 1

If a page is accessed via any query string, $_SERVER['QUERY_STRING'] fetches that query string.
for example, if you call url in your browser like this
http://example.com/index.php?name=msk&job=developer
then $_SERVER['QUERY_STRING'] contain following data
"name=msk&job=developer"
and explode() used to convert string to array where delimeter is &
$query = explode('&', $_SERVER['QUERY_STRING']);
now $query contain array with following data
Array
(
[0] => "name=msk"
[1] => job=developer"
)
.
$params = array(); //created to hold $_SERVER['QUERY_STRING'] array of strings
foreach ($query as $param) {
list($name, $value) = explode('=', $param, 2);
//above line try to convert "name=msk" into array like this ["name"] => array([0] = msk)
//list() function is used to assign values to a list of variables in one operation.
$params[urldecode($name)][] = urldecode($value);
}
$params contain following array data
(
["name] => Array
(
[0] => msk
)
[job] => Array
(
[0] => developer"
)
)
echo json_encode($params);
json_encode() used for converting php array to JSON
{"\"name":["msk"],"job":["developer\""]}
and come to your doubt
$param is just a loop iterator
$params is array used for holding $_SERVER['QUERY_STRING'] data