php - 为foreach（）提供了无效的参数(Invalid argument supplied for foreach())

Question

It often happens to me to handle data that can be either an array or a null variable and to feed some foreach with these data.

(我经常碰巧处理可以是数组或null变量的数据，并用这些数据提供一些foreach信息。)

$values = get_values();

foreach ($values as $value){
  ...
}

When you feed a foreach with data that are not an array, you get a warning:

(当为foreach提供非数组数据时，会收到警告：)

Warning: Invalid argument supplied for foreach() in [...]

(警告：[...]中为foreach（）提供了无效的参数)

Assuming it's not possible to refactor the get_values() function to always return an array (backward compatibility, not available source code, whatever other reason), I'm wondering which is the cleanest and most efficient way to avoid these warnings:

(假设不可能将get_values()函数重构为始终返回数组（向后兼容性，不可用的源代码，无论其他原因），我想知道哪种是避免这些警告的最干净，最有效的方法：)

• Casting $values to array

  (将$values为数组)

• Initializing $values to array

  (初始化$values到数组)

• Wrapping the foreach with an if

  (用if包装foreach)

• Other (please suggest)

  (其他（请建议）)

  ask by Roberto Aloi translate from so

Answer 1

Personally I find this to be the most clean - not sure if it's the most efficient, mind!

(我个人认为这是最干净的-不确定它是否最有效！)

if (is_array($values) || is_object($values))
{
    foreach ($values as $value)
    {
        ...
    }
}

The reason for my preference is it doesn't allocate an empty array when you've got nothing to begin with anyway.

(我偏爱的原因是，当您一无所有时，它不会分配空数组。)