PHP: Can include a file that file_exists() says doesn't exist

In my script, I set the include path (so another part of the application can include files too), check that a file exists, and include it.

However, after I set the include path, file_exists() reports that the file does not 开发者_运维百科exist, yet I can still include the same file.

<?php
  $include_path = realpath('path/to/some/directory');
  if(!is_string($include_path) || !is_dir($include_path))
  {
    return false;
  }
  set_include_path(
    implode(PATH_SEPARATOR, array(
      $include_path,
      get_include_path()
    ))
  );
  // Bootstrap file is located at: "path/to/some/directory/bootstrap.php".
  $bootstrap = 'bootstrap.php';

  // Returns "bool(true)".
  var_dump(file_exists($include_path . '/' . $bootstrap));
  // Returns "bool(false)".
  var_dump(file_exists($bootstrap));

  // This led me to believe that the include path was not being set properly.
  // But it is. The next thing is what puzzles me.

  require_once $bootstrap;
  // Not only are there no errors, but the file is included successfully!

I can edit the include path and include files without providing the absolute filepath, but I cannot check whether they exist or not. This is really annoying as every time a file that does not exist is called, my application results in a fatal error, or at best a warning (using include_once()).

Turning errors and warnings off is not an option, unfortunately.

Can anyone explain what is causing this behaviour?

file_exists does nothing more than say whether a file exists (and the script is allowed to know it exists), resolving the path relative to the cwd. It does not care about the include path.

Yes Here is the Simplest way to implement this

$file_name = //Pass File name 
if ( file_exists($file_name) )
            {
                echo "Exist";
            }
        else
            {
                echo "Not Exist";
            }