php - Can I use file_get_contents() to compare two files?

Question

I want to synchronize two directories. And I use

file_get_contents($source) === file_get_contents($dest)

to compare two files. Is there any problem to do this?

Answer 1

I would rather do something like this:

function files_are_equal($a, $b)
{
  // Check if filesize is different
  if(filesize($a) !== filesize($b))
      return false;

  // Check if content is different
  $ah = fopen($a, 'rb');
  $bh = fopen($b, 'rb');

  $result = true;
  while(!feof($ah))
  {
    if(fread($ah, 8192) != fread($bh, 8192))
    {
      $result = false;
      break;
    }
  }

  fclose($ah);
  fclose($bh);

  return $result;
}

This checks if the filesize is the same, and if it is it goes through the file step by step.

• Checking the modified time check can be a quick way in some cases, but it doesn't really tell you anything other than that the files have been modified at different times. They still might have the same content.
• Using sha1 or md5 might be a good idea, but this requires going through the whole file to create that hash. If this hash is something that could be stored and used later, then it's a different story probably, but yeah...