Register GET REST API route with multiple parameters

I’m trying to register a GET REST API route with multiple parameters with the following code:

register_rest_route( 'myplugin/v1', '/posts/?number=(?P<number>[d]+)&amp;offset=(?P<offset>[d]+)&amp;total=(?P<total>[d]+)', array(
    'methods'             => 'GET',
    'callback'            => 'my_rest_function',
    'permission_callback' => '__return_true',
    'args'                => array(
        'number' => array(
            'validate_callback' => function( $param, $request, $key ) {
                return is_numeric( $param );
            }
        ),
        'offset' => array(
            'validate_callback' => function( $param, $request, $key ) {
                return is_numeric( $param );
            }
        ),
        'total' => array(
            'validate_callback' => function( $param, $request, $key ) {
                return is_numeric( $param );
            }
        ),
    ),
) );

But, when I call it using for example:

https://example.com/wp-json/myplugin/v1/posts/?number=3&offset=0&total=3

I’m getting a No route was found matching the URL and request method. error.

What am I doing wrong?

Answers:

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Method 1

You don’t need to include query parameters in the endpoint. Just the path:

register_rest_route( 'myplugin/v1', '/posts', array(
    'methods'             => 'GET',
    'callback'            => 'my_rest_function',
    'permission_callback' => '__return_true',
    'args'                => array(
        'number' => array(
            'validate_callback' => function( $param, $request, $key ) {
                return is_numeric( $param );
            }
        ),
        'offset' => array(
            'validate_callback' => function( $param, $request, $key ) {
                return is_numeric( $param );
            }
        ),
        'total' => array(
            'validate_callback' => function( $param, $request, $key ) {
                return is_numeric( $param );
            }
        ),
    ),
) );

Method 2

The request should be a regular expression, but not HTML encoded. So, instead of & simply use &.

Also, the ? at the start of the URL query is interpreted as part of the regular expression, just meaning that the preceding / is optional. You have to escape it:

/posts/?number=(?P[d]+)&offset=(?P[d]+)&total=(?P[d]+)

To be absolutely sure you can escape the slashes, too, but AFAIK this is not necessary here.

You can test your regex at Regex101.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0