$string = "Test 2 test the filesize() fn, with data containing all the types like !@@##$%^&*():<>?|~+!;',.\][{}(special) chars, 12345(numeric) chars, and \n(newline char), \t(tab), \0, \r and so on........\0";
echo "-- opening the file in 'w' mode and get the size --\n";
$file_handle = fopen($filename, "w");
var_dump( strlen($string) ); //strlen of the string
fwrite($file_handle, $string);
fclose($file_handle);
var_dump( filesize($filename) ); //size of the file = strlen of string
clearstatcache();
echo "-- opening the file in 'wt' mode and get the size --\n";
$file_handle = fopen($filename, "wt");
var_dump( strlen($string) ); //strlen of the string = 191 bytes
fwrite($file_handle, $string);
fclose($file_handle);
var_dump( filesize($filename) ); //size of the file = 192 bytes != strlen of string
clearstatcache();
echo "-- opening the file in 'a' mode, adding data and checking the file --\n";
$file_handle = fopen($filename, "a");
fwrite($file_handle, "Hello, world");
fclose($file_handle);
var_dump( filesize($filename) ); //204 bytes
clearstatcache();
echo "-- opening the file in 'at' mode, adding data and checking the file --\n";
$file_handle = fopen($filename, "at");
fwrite($file_handle, "Hello, world\n");
fclose($file_handle);
var_dump( filesize($filename) ); //218 bytes
clearstatcache();
echo "-- creating a hole and checking the size --\n";
$file_handle = fopen($filename, "a");
var_dump( ftruncate($file_handle, 220) ); //creating 4 bytes of hole
fclose($file_handle);
var_dump( filesize($filename) ); //220 bytes
clearstatcache();
echo "-- writing data after hole and checking the size --\n";
$file_handle = fopen($filename, "a");
fwrite($file_handle, "Hello\0"); //wrting 6 bytes of data
fclose($file_handle);
var_dump( filesize($filename) ); //226 bytes
clearstatcache();
echo "-- opening the existing file in write mode --\n";