How to pass an array via $_GET in php?

Question

How can I pass one or more variables of type array to another page via $_GET?

I always passed variable values in the form ?a=1&b=2&c=3

What about passing a=[1,2,3] ?

Do I need to write a for loop and append all the values?

Thanks

Answer 1

You can use the [] syntax to pass arrays through _GET:

?a[]=1&a[]=2&a[]=3

PHP understands this syntax, so $_GET['a'] will be equal to array(1, 2, 3).

You can also specify keys:

?a[42]=1&a[foo]=2&a[bar]=3

Multidimentional arrays work too:

?a[42][b][c]=1&a[foo]=2

http_build_query() does this automatically:

http_build_query(array('a' => array(1, 2, 3))) // "a[]=1&a[]=2&a[]=3"

http_build_query(array(
    'a' => array(
        'foo' => 'bar',
        'bar' => array(1, 2, 3),
     )
)); // "a[foo]=bar&a[bar][]=1&a[bar][]=2&a[bar][]=3"

---

An alternative would be to pass json encoded arrays:

?a=[1,2,3]

And you can parse a with json_decode:

$a = json_decode($_GET['a']); // array(1, 2, 3)

And encode it again with json_encode:

json_encode(array(1, 2, 3)); // "[1,2,3]"

---

Dont ever use serialize() for this purpose. Serialize allows to serialize objects, and there is ways to make them execute code. So you should never deserialize untrusted strings.

Answer 2

You can pass an associative array to http_build_query() and append the resulting string as the query string to the URL. The array will automatically be parsed by PHP so $_GET on the receiving page will contain an array.

Example

$query_str = http_build_query(array(
    'a' => array(1, 2, 3)
));

Answer 3

$city_names = array(
    'delhi',
    'mumbai',
    'kolkata',
    'chennai'
);
$city_query = http_build_query(array('city' => $city_names));

this will give you:

city[0]=delhi&city[1]=mumbai&city[2]=kolkata&city[3]=chennai

if you want to encode the brackets also then use the below code:

$city_query = urlencode(http_build_query(array('city' => $city_names)));

Output:

city%255B0%255D%3Ddelhi%26city%255B1%255D%3Dmumbai .....

Reference: http_build_query, urlencode