php - Collapse on unique value which adding up the second in 2D array -

i have loop adds array of 2 values main array.

how can merge of arrays in main array have same first values while @ same time add values of second?

$maindata = array() ; //loop...  $cres = $dbh->query("select overdue _credit_control_overdue entityid = $entityid") ;         $currentowed = $cres->fetchcolumn() ;         $dbh->exec("replace _credit_control_overdue (entityid, overdue) values ('$entityid', '$remaining')") ;         $totalremaining += $remaining ;          array_push($maindata, array($entityid, $remaining)) ; //end of loop 

in many cases $entityid same, , $remaining different.

now need function similar array_unique leave me unique $entityid $remaining values added up, left e.g. 2339, 83572.60.

hope have explained clearly!

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this output desire:

array ( [0] => array ( [0] => 2499 [1] => 5314.50 ) [1] => array ( [0] => 639 [1] => 75.00 ))

i.e array ( [0] => uniqueid [1] => sum )

the best way first build associative array (hash) using $entityid keys (which give unique entry each one) , accumulated totals of $remaining values:

// initialise hash before looping $perentitytotals = array();  /* loop ... */  // add $remaining value appropriate entity's total // if key doesn't yet exist, created value $remaining $perentitytotals[$entityid] += $remaining;  /* end loop */ 

to re-format asked for, you'll need manipulate hash:

$maindata = array(); foreach ( $perentitytotals $entityid => $total ) {     $maindata[] = array($entityid, $total); } 

the below equivalent, harder read:

$maindata = array_map(     null,             // see example #4 on http://php.net/array_merge     array_keys($perentitytotals),     array_values($perentitytotals)  );