Read and write file with one fopen-CodePudding

With the following code I would like to read a number from file, increase it, an write back.

      $DATdatei = fopen("$dir$datFile", "rw ");       
      $count = (int) fgets($DATdatei, 5000);     
      $count  ;
      fwrite($DATdatei, $count);
      fclose($DATdatei);

But on writing back the number will be appended to the old number. I will get 1, then 12, and then 1213 ... How to avoid it.

CodePudding user response：

After the fgets(), the file pointer will remain the the end of the file.

fwrite() will write it's data at that pointer.

Use a rewind() call to set the file pointer to the beginning, to overwrite the content:

rewind — Rewind the position of a file pointer

<?php

      $DATdatei = fopen("$dir$datFile", "rw ");
      $count = (int) fgets($DATdatei);
      $count  ;
      
      rewind($DATdatei);
      fwrite($DATdatei, $count);
      fclose($DATdatei);