security - Where can Null Byte Injection affect my PHP web app in a realistic setting? -

i've read php section on http://projects.webappsec.org/null-byte-injection.

the example provides pretty dumb - mean, why ever want include file based on outside param without checking first (for directory traversal attacks, one)?

so, if following standard php security practices, such as

• encoding user entered data on display
• validating user entered stuff works files
• preventing crsf
• not running uploads via executes php
• etc

can provide real life example or common mistake of php developers problem can occur?

thanks

upate

i'm trying make break, , have tried.

// $filename public $filename = "some_file\0_that_is_bad.jpg";  $ext = pathinfo($filename, pathinfo_extension);  var_dump($filename, $ext); 

which outputs

string(26) "some_file�_that_is_bad.jpg" string(3) "jpg" 

i believe part of fun null byte injection simple validation may not enough catch them

e.g. string "password.txt\0blah.jpg" ends ".jpg" far scripting language concerned .. when passed c based function ( such many system functions) gets truncated "password.txt"

this means simple check may not safe. (this pseudocode, not php)

 if ( filename.endswith(".jpg") ) { some_c_function(filename); } 

instead may have do

 filename = break_at_null(filename);  if ( filename.endswith(".jpg") ) { some_c_function(filename); } 

now doesn't matter c function .. examples in cited article may have need file reading functions, database accesses, system calls, etc.