Correcting a TXT file when the user does not modify the data

The TXT file is not updated when the user of the program modifies the data without modifying it
Again back to the page, the user whether or not to modify the data are important to save, I set the JS hint, but million a bit wrong, the data is all gone, I want to write only the modified data in the file, if the value of the array to determine the null is not executed fwrite, but does not work, ask Daniel's advice

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     $filename = "AAPvaleurs.txt";$file _hwnd=fopen ($filename, "R");$content = Fread ($file _hwnd, FileSize ($filename));Fclose ($file _hwnd);$AAP 2 = unserialize ($content);?> 
   

  
  
  

  
  
 
   
 
    
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