Retrieve data from text file...stuck...

The solution james438 proffered will work, but is far from optimal. It is very memory-intensive if you have a lot of data, since it loads it all into memory at once. I strongly agree with the opinions expressed thus far about how much easier and more efficient this would be with a proper database. However, here is a somewhat better way of doing it using a buffer:

Code:

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define('BUF_SIZ', 128);

define('TYPE_COLUMN', 0);
define('YEAR_COLUMN', 1);
define('ID_COLUMN', 2);
define('VALUE_COLUMN', 3);

function select_from_file($get, $where, $val, $multiple = false) {
  $col %= 4;
  $r = $multiple ? array() : '';
  $f = open('yourfile.dat', 'r');

  for($current_line = '', $next_line = '', $pos; !feof($file);) {
    while(($pos = strpos($current_line, "\n")) === false)
      $next_line .= fread($f, BUF_SIZ);
    $next_line = str_replace("\r", '', $next_line);
    list($current_line, $next_line) = explode("\n", $next_line, 2);
    if($current_line) {
      $current_line = explode(' ', $current_line);
      if($current_line[$where] == $val)
        if($multiple)
          $r[] = $current_line[$get];
        else {
          $r = $current_line[$get];
          break 2;
        }
    }
  }
  fclose($f);
  return $r;
}

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E.G.:

Code:

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select_from_file(VALUE_COLUMN, ID_COLUMN, 2099) + select_from_file(VALUE_COLUMN, ID_COLUMN, 2641)

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is -225816.67. You can also use it for other columns; select_from_file(TYPE_COLUMN, VALUE_COLUMN, '-226930.95') will return '#IB', and select_from_file(VALUE_COLUMN, TYPE_COLUMN, '#IB', true) will return an array of values from rows that begin with #IB (if you don't pass the $multiple argument, only the first one will be selected).

Untested.

Take your time! I am very thankful for the help so far and don't feel pressure to deliver. I am the one who will be using this for various data.

I updated the script one last time to allow for unlimited identifiers, but I don't plan on doing any more work with it. There is plenty there in the script for you to learn from.

I really don't like the script much any more despite all I have learned from it in the process. This was good practice for me too. The code I wrote is too bulky. It is taxing on the server to say the least and in my experience these types of programs are just not as secure as databases. MySQL can do the same thing in one short line that is far easier to understand. The single MySQL line that Twey showed you above is all you really need.

Lastly, and most importantly, this script does not teach good coding practices, so listen to Twey.

Quote:

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The single MySQL line that Twey showed you above is all you really need.

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What MySQL line? That was a call to my function :p

But yes, in MySQL it's as simple as:

Code:

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list($value) = mysql_fetch_array(mysql_query('SELECT value FROM yourtable WHERE id = 2099;'), MYSQL_NUM);

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James superthanks for your help. Very greatful! I might consider mysql but will wait...it is a bit too much for me right now.

Twey, here is my test code but it doesn't return anything...

Code:

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<?PHP


define('BUF_SIZ', 128);

define('TYPE_COLUMN', 0);
define('YEAR_COLUMN', 1);
define('ID_COLUMN', 2);
define('VALUE_COLUMN', 3);

function select_from_file($get, $where, $val, $multiple = false) {
  $col &#37;= 4;
  $r = $multiple ? array() : '';
  $f = open('file.dat', 'r');

  for($current_line = '', $next_line = '', $pos; !feof($file);) {
    while(($pos = strpos($current_line, "\n")) === false)
      $next_line .= fread($f, BUF_SIZ);
    $next_line = str_replace("\r", '', $next_line);
    list($current_line, $next_line) = explode("\n", $next_line, 2);
    if($current_line) {
      $current_line = explode(' ', $current_line);
      if($current_line[$where] == $val)
        if($multiple)
          $r[] = $current_line[$get];
        else {
          $r = $current_line[$get];
          break 2;
        }
    }
  }
  fclose($f);
  return $r;
}


select_from_file('#IB', '0', '2099');

?>

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You've used it wrong. It takes three arguments, in the order of an SQL query: the column to get, the column to check, and the value that the checked column must have in order to match. The first two arguments should be *_COLUMN constants as defined at the top of the file. You'll also probably need to change 'file.dat' in the function to the name of your text file.

Got this piece of code from another forum. Any comments in it? (memory perspective etc):

Code:

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<?PHP


$contents = file('file.txt');

foreach($contents as $line_value)
{

list($cat, $int, $id, $num) = explode("\t", $line_value);

    $cat = str_replace('#', '', $cat);

    $number[$cat][$int][$id] = trim($num);
}

//echo '<pre>' . print_r($number, true) . '</pre>';


echo $number['UB'][-1][1650]*2;// returns -81219.00

// similarly $number['UB'][-1][1229]; will return 14100.00

?>

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As with james438's code, it loads the whole file into memory at once.

Possible to modify for better memory handling?

Aa I see. There are no column constants as in categories in my file...Well I have got some working solutions to continue my journey with.

Quote:

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Originally Posted by Twey

You've used it wrong. It takes three arguments, in the order of an SQL query: the column to get, the column to check, and the value that the checked column must have in order to match. The first two arguments should be *_COLUMN constants as defined at the top of the file. You'll also probably need to change 'file.dat' in the function to the name of your text file.

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