int fwrite ( resource handle , stringstring [, int $length ] )

<?php
   file = fopen("/PhpProject/sample.txt", "w");
   echo fwrite(file, "Hello Tutorialspoint!!!!!");
   fclose($file);
?>

25

<?php
   filename = "/PhpProject/sample.txt";somecontent = "Add this to the file\n";

   if(is_writable(filename)) {
      if(!handle = fopen(filename, 'a')) {
         echo "Cannot open file (filename)";
         exit;
       }
   if(fwrite(handle,somecontent) === FALSE) {
      echo "Cannot write to file (filename)";
      exit;
   }
   echo "Success, wrote (somecontent) to file (filename)";
   fclose(handle);

   } else {
      echo "The file $filename is not writable";
   }
?>

Success, wrote (Add this to the file) to file (/PhpProject/sample.txt)