When I do a readdir in a directory, Php forget some files

My directory have about 3000 files
size of files: 1.4Mo
type: sgi (pictures)
name of files: quad.xxxx.sgi (xxxx is a number, ie 0001) 

I've done tests on this directory, and listed files are never the same. Sometimes, Php forget files, but forgotten files are not the same one time to another.

Is there limits on the use if readir function?

my code for listing files is:

$directory_src = @opendir("/tmp"); 
while($iden_dir = @readdir($directory_src)) 
{ 
    echo "$iden_dir<BR>"; 
} 
@closedir($directory_src);