Description
bool 
is_readable ( string filename )
     Returns TRUE if the file or directory specified by 
     filename exists and is readable.
    
     Keep in mind that PHP may be accessing the file as the user
     id that the web server runs as (often 'nobody'). Safe mode
     limitations are not taken into account.
    
     
Example 1. is_readable() example 
<?php $filename = 'test.txt'; if (is_readable($filename)) {     echo 'The file is readable'; } else {     echo 'The file is not readable'; } ?>
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    Note: The results of this 
function are cached. See clearstatcache() for 
more details.
Tip: As of PHP 5.0.0 this function
can also be used with some URL wrappers.  Refer to 
Appendix M for a listing of which wrappers support 
stat() family of functionality.
     See also is_writable(), 
     file_exists(), and
     fgets().