<?php
 
// your data
 
$days[] = <<<__DATA
1|24-jan-11|n1|89|17|81|6|40
2|24-jan-11|n1|21|15|42|67|11
3|24-jan-11|n1|31|17|45|70|69
4|24-jan-11|n1|74|88|47|56|14
__DATA;
 
$days[] = <<<__DATA
5|28-jan-11|n2|31|25|75|37|84
6|28-jan-11|n2|15|4|20|34|68
7|28-jan-11|n2|19|15|81|14|67
8|28-jan-11|n2|47|17|15|71|14
__DATA;
 
foreach($days as &$d){
  $d = explode("\n", $d);
  array_walk($d, function(&$v){ $v = explode('|', $v); });
}
 
// -----
 
$pairs = array();
foreach($days[0] as $day){
  $len = count($day);
  for($i=3;$i<$len;$i++)
    for($j=$i+1;$j<$len;$j++){
      $key = $day[$j] > $day[$i] ? "{$day[$i]}|{$day[$j]}" : "{$day[$j]}|{$day[$i]}";
      $pairs[$key] = $day[0];
    }
} 
 
foreach($days[1] as $day){
  $len = count($day);
  for($i=3;$i<$len;$i++)
    for($j=$i+1;$j<$len;$j++){
      $key = $day[$j] > $day[$i] ? "{$day[$i]}|{$day[$j]}" : "{$day[$j]}|{$day[$i]}";
      if(isset($pairs[$key]))
        echo "\"{$day[$i]}\" and \"{$day[$j]}\" in the row \"{$pairs[$key]}\" and \"{$day[0]}\"\n";
    }
}
 

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