不是很漂亮，但是这里是我如何使用嵌套的foreach来做到这一点；

not pretty but heres how I would do it with a nested foreach;

$aStartingArray = array();
$aStartingArray[] = array('source'=>'ABC', 'target' => 'DEF', 'total_volume' => 10); 
$aStartingArray[] = array('source'=>'ABC', 'target' => 'GHI', 'total_volume' => 5); 
$aStartingArray[] = array('source'=>'ABC', 'target' => 'DEF', 'total_volume' => 5); 


$aSortedArray = array();

foreach ($aStartingArray as $aArray) {

    $bSet = false;

    foreach ($aSortedArray as $iPos => $aTempSortedArray) {

        if(
            $aTempSortedArray['source'] == $aArray['source'] && 
            $aTempSortedArray['target'] == $aArray['target']){

            $aSortedArray[$iPos]['total_volume'] += $aArray['total_volume'];

            $bSet = true;
        }

    }

    if(!$bSet) {

        $aSortedArray[] = array(
            'source' => $aArray['source'], 
            'target' => $aArray['target'], 
            'total_volume' => $aArray['total_volume']
            );
    }
}


var_dump($aSortedArray);