PHP Warning: mysql_free_result() expects parameter 1 to be resource solution

PHP Warning: mysql_free_result() expects parameter 1 to be resource solution

When using PHP to connect to the MySQL database, the result set obtained by executing the query statement needs to be released using the function mysql_free_result(). to avoid memory leaks. But sometimes we encounter this error message: PHP Warning: mysql_free_result() expects parameter 1 to be resource. What's the problem? how should I solve this?

1. Problem Analysis

Let’s first analyze the meaning of this error message: mysql_free_result() expects the first parameter passed in to be a resource type value. What is the resource type? In PHP, using the mysql_query() function to execute a query statement will return a value of the result set resource type. In other words, the return value of the mysql_query() function, which is the value of the result set resource type, should be passed in the first parameter passed into the mysql_free_result() function.

If we encounter this error message, it means that the correct parameter is not passed in the first parameter passed into the mysql_free_result() function. This parameter should actually be the result set resource type returned by the mysql_query() function. value. Therefore, this error message reminds us that we need to check whether the mysql_query() function is used correctly in the code and confirm that its return value is indeed a resource type value.

2. Solution

To solve this problem, we need to start from two aspects: one is to check the code, and the other is to understand the usage specifications of the mysql_query() function.

2.1 Check the code

When checking the code, we need to find the mysql_query() function and mysql_free_result() function, and whether the parameters passed between these two functions are correct. If there is a problem with the parameters passed, an error will be reported. We need to confirm the following points in the code:

• Whether the mysql_query() function is correctly used to connect to the database and execute the query statement
• Whether the result set returned by the mysql_query() function is used The value of the resource type is used as a parameter of the mysql_free_result() function
• Whether the mysql_query() function returns the result set and is paused for a period of time before executing the mysql_free_result() function. This period of time may cause the result set resource to become invalid.

If there are no problems with the above points, then it is likely that the result set resource returned by the mysql_query() function is invalid. At this time, we need to carefully observe the usage specifications of the mysql_query() function.

2.2 Understand the usage specifications of the mysql_query() function

The first thing to note is that the mysql_query() function was deprecated after PHP 5.5.0 and was deprecated after PHP 7.0.0. delete. It is currently recommended to use the mysqli_query() function or PDO's prepare() and execute() functions instead. Therefore, we need to be careful when using the mysql_query() function to try to avoid problems, or use the safer and more stable mysqli_query() function or PDO's prepare() and execute() functions.

Secondly, it should be noted that the result set resource type value returned by the mysql_query() function is only valid when the function is called, and only when the query statement is not a SELECT statement, a non-resource type value will be returned. value. Therefore, we need to confirm whether the mysql_query() function is used correctly in the code and check whether the value returned is a resource type value.

Finally, what you need to know is that the value of the result set resource type returned by the mysql_query() function will be automatically released as long as the mysql_query() function is executed. Therefore, if we execute the mysql_free_result() function immediately after the mysql_query() function returns the result set, a parameter type error will occur.

In summary, in order to avoid the error PHP Warning: mysql_free_result() expects parameter 1 to be resource, we need to pay attention to the following points when using the mysql_query() function:

• Try to avoid using the mysql_query() function, and choose the safer and more stable mysqli_query() function or PDO's prepare() and execute() functions
• Confirm that the mysql_query() function is used correctly in the code, and Check whether the return value is a resource type value
• Only use the mysql_query() function when confirming that the query statement is a SELECT statement, and release the returned result set resource type value in a timely manner

In short, when using PHP to connect to the MySQL database, we need to pay attention to comply with the specifications, avoid errors, and ensure the correctness and stability of the code.

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