php 数组合并的问题? 400 报错

<?php
$arr1 = array("1月","3月","4月");
$arr1date=array("100","200","300");

$arr2 = array("1月","2月","5月");
$arr2date=array("300","400","500");

$arr3 =array("1月","2月","3月","4月","5月");

$a1 = array_combine($arr1,$arr1date);
$a2 = array_combine($arr2,$arr2date);
$arr1date1 = $arr1date2 =array();

foreach ($arr3 as $v){
	if(isset($a1[$v])){
		$arr1date1[] = $a1[$v];
	}else{
		$arr1date1[] = "0";
	}
	if(isset($a2[$v])){
		$arr2date1[] = $a2[$v];
	}else{
		$arr2date1[] = "0";
	}

}
print_r($arr1date1);
print_r($arr2date1);
?>