php将$arr 二维数组的所有第二层合并后返回

array_merge() 将一个或多个数组的单元合并起来，一个数组中的值附加在前一个数组的后面。返回作为结果的数组。
但是只能合并第一层,却无法合并二级数组的二维部分
我写了点代码,感觉很不好,希望高手指更好的方法

<?php
$arr=array(
	"0" => array(
		"44" => array("id" => 44,"name" => '九鱼图'),
		"45" => array("id" => 45,"name" => '锦鲤')
		),
	"1" => array(
		"49" => array("id" => 49,"name" => '百福图'),
		"50" => array("id" => 50,"name" => '蝙蝠')
	),
	"2" => array(
		"40" => array("id" => 40,"name" => '古钱'),	
		"41" => array("id" => 41,"name" => '葫芦')
	)
);
//将$arr 二维数组的所有第二层合并后返回
function array_merge_array($arr)
{
	$str="$"."son_arr=array_merge(";
	foreach($arr as $k => $v)
	{$str.='$arr['.$k.'],';}
	$str.=");";
	eval(str_replace(',)',')',$str));
	return $son_arr;
}
print_r(array_merge_array($arr));

/*
得到结果
Array
(
    [0] => Array
        (
            [id] => 44
            [name] => 九鱼图
        )

    [1] => Array
        (
            [id] => 45
            [name] => 锦鲤
        )

    [2] => Array
        (
            [id] => 49
            [name] => 百福图
        )

    [3] => Array
        (
            [id] => 50
            [name] => 蝙蝠
        )

    [4] => Array
        (
            [id] => 40
            [name] => 古钱
        )

    [5] => Array
        (
            [id] => 41
            [name] => 葫芦
        )

)

*/
?>