How to get override the WP Admin Syndication feed limit for a custom feed?

Question

I need to override the setting in the WP Admin for the number of recent posts in the Syndication settings under General -> Admin.

I'm using the following code, which gets all posts, but I don't need that many. Can someone tell me how to retrieve 50 posts?

function no_limits_for_feed( $limits ) {
    return '';
}

add_filter( 'post_limits', 'no_limits_for_feed' );

Answer 1

This is no normal filter. It's a filter_ref_array.

// Use this to alter your limit:
add_filter( 'post_limits', create_function( '$a', "return 'LIMIT $start, 10';" ) );

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EDIT

After I saw that this got marked as solution, I want to show you a more "best practice"-approach:

function alter_feed_post_limits( $limits )
{
    return " LIMIT 0,50";
}
add_action( 'post_limits', 'alter_feed_post_limits' );