php - array_filter的回调函数内非空数组变为null

Question

这个问题已经有答案了:

Accessing outside variable using anonymous function as params (2 个回答)

已关闭 7 年前。

我正在尝试比较数组内的值，该值是在调用 array_filter 之前初始化的。

当控制流进 array_filter 的回调函数时，数组不为空，但变为 null。这可能是什么原因？

$stream = $stream_list[$i]['@attributes']; // IS ARRAY

$chargeable_feature = array_filter($applicable_conversions,function($conversion) {
     return $conversion['FeatureName'] == $stream['FeaturesUsed'];
     // STREAM BECOMES NULL HERE
});

Answer 1

$stream = $stream_list[$i]['@attributes']; // IS ARRAY

$chargeable_feature = array_filter($applicable_conversions,function($conversion) use ($stream) {
     return $conversion['FeatureName'] == $stream['FeaturesUsed'];
});