How PHP handles errors obtained in Redis

PHP Redis is a very popular PHP extension that allows PHP programmers to use the Redis NoSQL database. In the process of using Redis in PHP Redis, we may encounter various errors, among which retrieval errors are one of the very common errors. This article will introduce how to deal with retrieval errors in PHP Redis.

Get errors refer to situations where you try to get certain values ​​but fail when using Redis. There are many situations when getting errors, such as the Redis server is not connected, the key value does not exist, the wrong data type, etc. Here's how to deal with these common acquisition errors.

1. The Redis server is not connected

When using Redis, if the Redis server is not connected, then we cannot obtain any data. We need to make sure we have successfully connected to the Redis server before using Redis. You can use the following code to check whether Redis is connected:

if (!$redis->ping()) {
    // connect to Redis
}

If the Redis server is not connected, we need to call the $redis->connect() method to reconnect:

if (!$redis->ping()) {
    $redis->connect('127.0.0.1', 6379);
}

2. Key value does not exist

When obtaining a key value that does not exist, Redis will return false. We need to check whether the return result is false. If so, it means that the key value does not exist:

$value = $redis->get('key');
if ($value === false) {
    // key does not exist
}

We can also use $redis->exists() The method checks whether the key value exists. If the return result is 1, it means that the key value exists:

if ($redis->exists('key')) {
    // key exists
}

3. Wrong data type

In Redis, each key value has a corresponding type of data. If we try to get the wrong data type, an error will be returned. The following are some common data types and corresponding acquisition methods:

• String type: $redis->get()
• Hash type: $redis->hget()
• List type: $redis->lindex()
• Collection type: $ redis->srandmember()
• Ordered collection type: $redis->zrange()

If we try to get an error data type, an error message similar to the following will be returned:

ERR Operation against a key holding the wrong kind of value

We need to ensure that the correct method is used when obtaining data, otherwise an error will occur.

4. Timeout error

When we obtain Redis data, if a timeout is set and the timeout has reached, Redis will automatically delete the relevant key values. At this point, if we try to get this key value, null will be returned. Therefore, we need to check whether the return result is null and whether there is an error message:

$value = $redis->get('key');
if ($value === null && $redis->getLastError()) {
    // timeout error
}

In the above code, if the return result is null and there is an error message ($redis->getLastError () method returns a non-empty string), indicating that a timeout error has occurred.

In summary, through the above introduction, we can see that handling acquisition errors in PHP Redis is not complicated. We only need to pay attention to checking the connection status before obtaining data to ensure that the key value exists and is used correctly. method. In addition, we need special processing for specific error types. For example, timeout errors require checking error information.

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