Question

I try to combine result from several queries and put them into an array. I found there are some duplications exist. What I want to do is keep the first record and remove the following same records if duplication exist. I want to write a function to filter array and remove duplications. Can anyone help me with it? thanks

array(4) {
  [0]=>
  array(14) {
    ["user_id"]=>
    string(7) "2620613"
    ["first_name"]=>
    string(5) "Susan"
    ["last_name"]=>
    string(9) "Alexander"
    ["client"]=>
    string(7) "Pro"
    ["ssn"]=>
    string(9) "4234324"
    ["hiredate"]=>
    string(10) "2008-04-11"
    ["hra_id"]=>
    string(6) "43244"
    ["hra_date"]=>
    string(10) "2011-08-17"
    ["hra_maileddate"]=>
    NULL
    ["screening_id"]=>
    string(6) "3764551"
    ["screening_date"]=>
    string(10) "2011-08-12"
    ["screening_maileddate"]=>
    NULL
    ["ref"]=>
    string(1) "D"
    ["mailable"]=>
    string(3) "Yes"
  }
  [1]=>
  array(14) {
    ["user_id"]=>
    string(7) "263453"
    ["first_name"]=>
    string(6) "Dharti"
    ["last_name"]=>
    string(6) "Surani"
    ["client"]=>
    string(7) "Pro"
    ["ssn"]=>
    string(9) "345325"
    ["hiredate"]=>
    string(10) "2002-04-29"
    ["hra_id"]=>
    string(6) "3455345"
    ["hra_date"]=>
    string(10) "2010-03-22"
    ["hra_maileddate"]=>
    NULL
    ["screening_id"]=>
    string(6) "234234"
    ["screening_date"]=>
    string(10) "2011-07-11"
    ["screening_maileddate"]=>
    NULL
    ["ref"]=>
    string(1) "D"
    ["mailable"]=>
    string(3) "Yes"
  }
  [2]=>
  array(14) {
    ["user_id"]=>
    string(7) "2685056"
    ["first_name"]=>
    string(4) "Alex"
    ["last_name"]=>
    string(2) "Hu"
    ["client"]=>
    string(7) "Pro"
    ["ssn"]=>
    string(9) "000005562"
    ["hiredate"]=>
    string(10) "2011-09-15"
    ["hra_id"]=>
    string(6) "528948"
    ["hra_date"]=>
    string(10) "2011-07-06"
    ["hra_maileddate"]=>
    NULL
    ["screening_id"]=>
    string(6) "377382"
    ["screening_date"]=>
    string(10) "2011-06-15"
    ["screening_maileddate"]=>
    NULL
    ["ref"]=>
    string(1) "D"
    ["mailable"]=>
    string(3) "Yes"
  }
  [3]=>
  array(14) {
    ["user_id"]=>
    string(7) "2685056"
    ["first_name"]=>
    string(4) "Alex"
    ["last_name"]=>
    string(2) "Hu"
    ["client"]=>
    string(7) "Pro"
    ["ssn"]=>
    string(9) "000005562"
    ["hiredate"]=>
    string(10) "2011-09-15"
    ["hra_id"]=>
    string(6) "528948"
    ["hra_date"]=>
    string(10) "2011-07-06"
    ["hra_maileddate"]=>
    NULL
    ["screening_id"]=>
    string(6) "377971"
    ["screening_date"]=>
    string(10) "2011-09-13"
    ["screening_maileddate"]=>
    NULL
    ["ref"]=>
    string(1) "E"
    ["mailable"]=>
    string(3) "Yes"
  }
}

I try to use the following function to remove duplications, but it doesn’t work very well and may cause error on some cases.

 $resultDE = array_merge($resultD1, $resultE1, $resultE2);
  function specified_array_unique($array) 
  { 
      for($i=0; $i<count($array); $i++){
        if(($array[$i]['user_id'] == $array[$i+1]['user_id']) && isset($array[$i+1]))
         unset($array[$i+1]); 
      }

      return $array; 
  } 

 var_dump(super_unique($resultDE));

Answer 1

You need to decide which array key you are going to use to determine whether the record is a duplicate or not. In the following example, you would pass this key into the second parameter.

EDIT I just made this MUCH more efficient..

function array_remove_duplicates ($array, $key) {
  $temp = array();
  foreach ($array as $k => $record) {
    if (isset($record[$key])) {
      // We're only going to filter records that actually have the supplied key present
      if (in_array($record[$key],$temp)) {
        // Key already exists, ignore this one
        unset($array[$k]);
      } else {
        // Key doesn't exist, add it to the tracking array
        $temp[] = $record[$key];
      }
    }
  }
  // we have filtered out the records we don't want so re-order the indexes and return the array
  return array_merge($array);
}

// ...and you could use it like this
$filteredArray = array_remove_duplicates($originalArray,'user_id');