[artist]

PHP Code:

#include <amxmodx>

native get_pl_value(id)

public plugin_init()
{
    register_clcmd("say / value", "functions")
}
public plugin_natives()
{
    set_native_filter("native_filter")
}
public native_filter(natives[], index, trap)
{
    if(equal(natives, "get_pl_value")) return PLUGIN_HANDLED
    return PLUGIN_CONTINUE
}
public functions(id)
{
    client_print(id, print_chat, "%i", get_pl_value(id))
} 


If there is no module with function get_pl_value, the message will output 0.
Is it possible to make it inferred -1?

[CrazY.]

I don't think it's possible, but you can use this very basic method:

new iPlVal = get_pl_value(id);

if (!iPlVal)
      iPlVal = -1;

Better check if the library exists.