nginx server with dynamic index is not executing php

i tried setting up my php backend and my vue on the same location. Based on the X-Requested-With header the server should decide if the backend would be used or the vue should be delivered. Now the delivery of the vue file is working, but the php is not executed.

info: at the position of X-URI the $uri is /index.php, but it is not running php

    # Backend
    if ($http_x_requested_with = "XMLHttpRequest") {
        set $INDEX "index.php";
        set $DOCOUMENTROOT "C:/server/web/www/altv_gadget/public";
        set $SERVING "LaminasMVC";
    }
    
    # Vue Frontend
    if ($http_x_requested_with != "XMLHttpRequest") {
        set $INDEX "index.html";
        set $DOCOUMENTROOT "C:/server/web/www/altv_gadget/dist";
        set $SERVING "Vue";
    }

    # Directory Indexes
    index $INDEX;

    # Document Root
    root $DOCOUMENTROOT;

    # Serving Header
    add_header X-Serving $SERVING;

    # Location
    location / {
        try_files $uri $uri/ /index.php$is_args$args /index.html$is_args$args;
    }

    add_header X-URI $uri;
        
    # For PHP files, pass to php_farm
    location ~ .php$ {
        add_header     X-PHP "1";
        fastcgi_pass   php_farm;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include        fastcgi_params;
    }

I hope somebody has an idea how to fix this.

Answer

I dont know what was my issue, but it seems to work know. For my specific solution i went with try_files $uri $uri/ /$INDEX$is_args$args; to use either my index.html or index.php based on my param.