Transform GraphQL fields into JSON to use them for filtering native PHP arrays

graphql-mini.php

<?php

/** A poor mans GraphQL fields parser
 *
 * Try to convert graphQL fields to JSON and then just use json_decode to produce an array.
 */
class Fields
{
        /** Parse GraphQL fields into an array */
        public static function parse($query)
        {
                $query = str_replace("{", "{\n", $query);
                $query = str_replace("}", "\n}\n", $query);
                $query = array_map("trim", explode("\n", $query));
                foreach ($query as $k => $line) {
                        // strip comments
                        $line = explode("#", $line);
                        $line = $line[0];
                        // skip opening or closing tags
                        if ($line === "{" || $line === "") {
                                continue;
                        }
                        // declare as object value
                        if (strpos($line, "{") !== false) {
                                $name = trim(str_replace("{", "", $line));
                                $query[$k] = '"' . $name . '": {';
                                continue;
                        }
                        if (strpos($line, "}") !== false) {
                                $query[$k] .= ',';
                                continue;
                        }
                        $query[$k] = '"' . $line . '": true,';
                }
                $query = implode("", $query);
                // cut last comma
                $query = substr($query, 0, -1);
                // cut trailing commas
                $query = str_replace(",}", "}", $query);
                // produce php array
                $retval = json_decode($query, true);
                if (is_null($retval)) {
                        throw new \Exception(sprintf("Error when parsing GraphQL fields: '%s'", $query));
                }
                return $retval;
        }

        /** Filter a PHP array with the GraphQL fields provided by parse() */
        public static function execute($query, $data)
        {
                $filter = self::parse($query);
                $result = array_intersect_key_recursive($data, $filter);
                return $result;
        }
}

function array_intersect_key_recursive($arr, $filter)
{
        $is_int = true;
        foreach ($arr as $k => $v) {
                if (!is_int($k) || !is_array($v)) {
                        $is_int = false;
                        break;
                }
        }

        if ($is_int) {
                foreach ($arr as $k => $v) {
                        $arr[$k] = array_intersect_key_recursive($v, $filter);
                }
                return $arr;
        }

        $retval = array();
        foreach ($filter as $key => $value) {
                if (!isset($arr[$key])) {
                        continue;
                }
                if (is_array($value)) {
                        $retval[$key] = array_intersect_key_recursive($arr[$key], $value);
                        continue;
                }
                $retval[$key] = $arr[$key];
        }
        return $retval;
}

The above piece of code parses a very small subset of GraphQL, dealing with fields, for example:

{
    name
    id
    #comment
    value {
        name
        id
    }
}

This will be naively converted to JSON, and parsed into a PHP array:

array (
  'name' => true,
  'id' => true,
  'value' =>
  array (
    'name' => true,
    'id' => true,
  ),
)

The array_intersect_key_recursive function is the glue that allows to use the above notation to filter possible untyped/non-object API responses that you may produce with your existing API. To use it to filter your API responses might be as simple as:

if (isset($_GET['graphql_query'])) {
    $response = Fields::execute($_GET['graphql_query'], $response);
}

The code is PHP 5.3+ compatible (might work on even older PHP versions). As said, it only supports a narrow subset of GraphQL field queries, doesn't implement any kind of AST parser, no references, objects, and many other things. It's usable only as a minimal filter that will reduce your API responses to fields which you define with GraphQL.

when calling $response = Fields::execute($_GET['graphql_query'], $response); what its response?

Try it

…

On Thu, Jan 27, 2022, 22:15 Jorge ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ when calling $response = Fields::execute($_GET['graphql_query'], $response); what its response? — Reply to this email directly, view it on GitHub <https://gist.github.com/e1414880099e0e5a90d87d56736bd87f#gistcomment-4044746>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABY7EHJ2VP3FAK3Q7TQ6J3UYGYW7ANCNFSM5M7B5VWQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>