$json = '[{"username":"用户名已存在","state":"false"},{"passw":"密码强度较弱","state":"true"},{"repassw":"密码一致","state":"true"},{"email":"此邮箱已被注册","state":"false"}]';

$json = json_decode($json);

$array = array();

foreach ($json as $key => $value) {

var_dump($value);

foreach ($value as $k => $v) {

# code...

$array[$k] = $v;

}

}

var_dump($array);

for($i=0;$i<count($arr);$i++){
    $newArr[]=$arr[$i];
}