How to check if a library exist in a controller?

PHP Code:

if(file_exists("../libraries/myapp/" . ucfirst($library_name).".php")) { 


This code is not working for me.
It is written inside of a controller.

I have a default library and some special libraries.
If special libraries are just the controller names.

If they exist, they should be loaded. Or the default one should be loaded.

PHP Code:

if(file_exists("../libraries/myapp/" . ucfirst($library_name).".php")) {
    $this->load->library("myapp/".$library_name);
}
else {
    $this->load->library("app_default_library");
} 


What is the right way to check the existence of a library?

Check if object is available:

PHP Code:

$is_loaded = is_object(@$this->upload) ? TRUE : FALSE;// @ sign suppressed error if object didn't exist
var_dump($is_loaded);
exit; 


Now you just need to make your own method that take a parameter as name of library:

PHP Code:

private function is_lib($lib)
{
    return is_object(@$this->{$lib}) ? TRUE : FALSE;
} 


PHP is_object function.

How can we use

PHP Code:

$this->{$lib} 


?
Dont we need to load it first?

PHP Code:

$this->load->library($lib); //This lines throws 500 Internal Server Error. Because that library is not available. 


I understand that you want first to check if library loaded.
If not than you need to load, else you just use that library:

PHP Code:

public function some_other_method()
{
    if ( ! $this->is_lib($lib))
    {
        $this->load->library($lib);
    }
    // rest of your code
}

private function is_lib($lib)
{
    return is_object(@this->{$lib}) ?: FALSE;
}