<?php

// FILENAME: dataarray.PHP

   $linenumber['number']=array(
                  'dt'=>[str date],
                  'ts'=>[int timestamp],
                  'lat'=>[int latitude], 
         'long' =>[int longitude],
         'alt' =>[int altitude]);

?>

<?php
// FILENAME: /DATAARRAY.PHP

// where is the data file?
$data_file = './example.dat'; // relative path.

// you can set the interval in seconds.  Default is 5 seconds.
// e.g. http://www.example.com/dataarray.php?interval=2
$interval = 5;
if( isset($_REQUEST['interval']) )
{
  $interval = intval( $_REQUEST['interval'] );
  if( $interval<1 )
    $interval = 5; // invalid value, so use default.
}

// open tag for the table of records.
echo '<table style="border-collapse:collapse;" cellspacing="0" cellpadding="3" border="1">' .
     '<tr><th>date</th><th>time</th><th>latitude</th><th>longitude</th><th>altitude</th></tr>';

// open the file for reading.
if( !$fp=@fopen($data_file, 'rb') )
  trigger_error( "Cannot open file <var>$data_file</var> for reading." );
// while not EOF, grab a line, process the data and print the matching line.
while( !feof($fp) )
{
  $line = trim( @fgets($fp, 4096) );
  if( $line )
  { // process the line of data.
    $tmp = explode( "\t", $line ); // $tmp[1] is the `time` data.
    if( !isset($ts) )
    { // do this once and only with the FIRST line.
      $time_str = $tmp[1];
      $ts       = strtotime( $tmp[1] );
    }
    if( $tmp[1] == $time_str )
    { // matching line.
      // alternate the row (background) colours.
      $bc = ( $bc==' style="background-color:#dadada;"' ? null : ' style="background-color:#dadada;"' );
      echo "<tr><td$bc>$tmp[0]</td><td$bc>$tmp[1]</td><td$bc>$tmp[2]</td><td$bc>$tmp[3]</td><td$bc>$tmp[4]</td></tr>";
      // set the next timestamp to look for.
      $ts       = strtotime( "+$interval seconds", $ts );  // adds [int interval] seconds to the previous unixtimestamp (UTS).
      $time_str = date( "H:i:s", $ts );  // formats the UTS into something like "13:44:20"
    }
  }    
}
// close the data file.
@fclose( $fp );

// if $data_file is empty, we say so...
if( !isset($time_str) ) // since this variable is set only if there was at least ONE row of data in the file.
  echo "<tr><td colspan=\"5\">No records found.</td></tr>";
// close the table of records.
echo "</table>";
?>