Array.php

<?php
# filepath src/

class MyArray
{

    public static function sumCountByIdentity($items, $identityKey, $countKey){
        $tmp = $newItems = [];
        foreach($items as $row){

            if( ! is_array($row) || !isset($row[$identityKey]) || !isset($row[$countKey]) ){
                throw new InvalidArgumentException('sub value of items must an array');
            }

            if( ! array_key_exists($row[$identityKey], $tmp) ){
                $tmp[$row[$identityKey]] = 0;
            }

            $tmp[$row[$identityKey]] += $row[$countKey];
        }

        foreach($tmp as $address => $count){
            $newItems[] = [ $identityKey => $address, $countKey => $count, ];
        }

        return $newItems;
    }
}

ArrayTest.php

<?php
# filepath tests/

include ('../src/Array.php');
class ArrayTest extends PHPUnit_Framework_TestCase
{
	public $items = array(
	     array("address"=>"美国", "count"=>123),
	     array("address"=>"美国", "count"=>34),
	     array("address"=>"中国", "count"=>2),
	     array("address"=>"中国", "count"=>20),
	     array("address"=>"法国", "count"=>345)
	);

    public $exceptValues = [ '美国'  => 157, '法国' => 345, '中国' => 22, ];

    public function testSumCountByIdentity(){

        $data = MyArray::sumCountByIdentity( $this->items, 'address', 'count');

        foreach($data as $row){
            $address = $row['address'];
            $count = $row['count'];
            $this->assertEquals($this->exceptValues[$address], $count);
        }
    }

    /**
     * @expectedException InvalidArgumentException
     */
    public function testSumCountByIdentityException1(){
        $arr = $this->items;
        $arr[] = "";

        MyArray::sumCountByIdentity($arr, 'address', 'count');
    }

    /**
     * @expectedException InvalidArgumentException
     */
    public function testSumCountByIdentityException2(){
        MyArray::sumCountByIdentity($this->items, 'address', 'ss');
    }

    /**
     * @expectedException InvalidArgumentException
     */
    public function testSumCountByIdentityException3(){
        MyArray::sumCountByIdentity($this->items, 'aaa', 'count');
    }
}