$mu=array(1=>"value","value1","value3");

$ke=json_encode($mu);

echo $ke;

输出结果：

{"1":"value","2":"value1","3":"value3"}

**************************************************************************************************

$mu=array(0=>"value","value1","value3");

$ke=json_encode($mu);

echo $ke;

输出结果：

["value","value1","value3"]

**************************************************************************************************

$mu=array(a=>"value","value1","value3");

$ke=json_encode($mu);

echo $ke;

输出结果：

{"a":"value","0":"value1","1":"value3"}