PHP Warning: Invalid argument supplied for mysql_fetch_array() solution

In the process of using PHP programming, we often encounter various error prompts. Among them, the PHP Warning: Invalid argument supplied for mysql_fetch_array() error is a relatively common error. This kind of error message usually indicates that the parameters of the mysql_fetch_array() function are incorrect, causing the function call to fail. So, how do we fix this error? This article will introduce in detail the solution to the PHP Warning: Invalid argument supplied for mysql_fetch_array() error.

First of all, we must understand the cause of this error. This error message indicates that the parameters were passed incorrectly when calling mysql_fetch_array(). There are usually two situations where this error occurs:

1. Parameters are not passed correctly: mysql_fetch_array() needs to receive a result set object as a parameter. If the result set object is not passed correctly, this error will occur. .
2. The result set object has been processed: If the result set object has been processed, this error will occur when mysql_fetch_array() is called again to obtain the database query results.

So, how to solve this error? The following are some common solutions:

Method 1: Check whether the parameters passed are correct

First, we need to check whether the parameters of the mysql_fetch_array() function are correct. Make sure the parameters passed are correct. You can try printing the parameters to see if there are errors.

Method 2: Check whether the result set object has been processed

After executing the query statement, we need to call the mysql_query() function to perform the query operation and use the returned result set object as mysql_fetch_array () parameter passing. However, before using the result set object, we need to check whether the result set object has been processed. If it has been processed, the mysql_fetch_array() function cannot be called again. This can be determined through the mysql_num_rows() function to determine whether the result set object is empty.

Method 3: Check whether the database is connected

If the PHP Warning: Invalid argument supplied for mysql_fetch_array() error occurs, you also need to check whether the database is successfully connected. If the database is not connected or the connection fails, the result set object returned by calling the mysql_query() function will be empty, causing the mysql_fetch_array() function to fail. You can use the mysql_connect() function and mysql_select_db() function to connect to the database.

Method 4: Use mysqli or PDO extension

If none of the above methods can solve the problem, you can consider using mysqli or PDO extension. Mysqli is a new extension in PHP5 and above. It supports both object-oriented and process-oriented programming methods, providing more functions and better efficiency. PDO is another database extension in PHP5 and above. It is an abstraction layer that can support multiple database types. Use mysqli or PDO extensions to avoid the PHP Warning: Invalid argument supplied for mysql_fetch_array() error.

To sum up, the PHP Warning: Invalid argument supplied for mysql_fetch_array() error is usually caused by incorrect parameters of the mysql_fetch_array() function. When solving this problem, you first need to check whether the parameters are correct, and then check whether the result set object has been processed and whether the database has been successfully connected. If none of the above methods solve the problem, you can consider using mysqli or PDO extensions. Of course, when this kind of mistake occurs, we should learn more about our own shortcomings, learn more and understand more, and avoid the same mistake from happening again.

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