if you need for theme you can use my function

function file_checker($file){
    //http://localhost/wordpress/wp-content/themes/THEMEName
    $location = get_template_directory_uri();// you can edit this <=
    $location = str_replace("http://","",$location);
    $location = str_replace("https://","",$location);
    $location = str_replace($_SERVER['HTTP_HOST'],"",$location);
    $location = $_SERVER['DOCUMENT_ROOT'].$location;
    $filename = $location.$file;
    
    if (file_exists($filename)) {
        return true;
    } else {
        return false;
    }
}

use

if(file_checker("/style.css")){
    echo "file Has";
}else{
    echo " Error Location , Check Your Code";
}

if you need for theme you can use my function

function file_checker($file){
    //http://localhost/wordpress/wp-content/themes/THEMEName
    $location = get_template_directory_uri();// you can edit this <=
    $location = str_replace("http://","",$location);
    $location = str_replace("https://","",$location);
    $location = str_replace($_SERVER['HTTP_HOST'],"",$location);
    $location = $_SERVER['DOCUMENT_ROOT'].$location;
    $filename = $location.$file;
    return (file_exists($filename));

}

use

if(file_checker("/style.css")){
    echo "file Has";
}else{
    echo " Error Location , Check Your Code";
}