Скачать или смотреть Resolving Trying to Get Property of Non-Object Error in PHP MySQL

Learn how to handle the `Trying to get property of non-object` error in your PHP scripts when working with MySQL data fetching through prepared statements.
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This video is based on the question https://stackoverflow.com/q/63632670/ asked by the user 'Damien Bourdonneau' ( https://stackoverflow.com/u/5232940/ ) and on the answer https://stackoverflow.com/a/63633266/ provided by the user 'CBroe' ( https://stackoverflow.com/u/1427878/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding and Fixing the Trying to Get Property of Non-Object Error

If you've ever encountered the error message Trying to get property 'f_text' of non-object in your PHP application, you're not alone. This error often occurs when fetching data from a MySQL database using prepared statements with the mysqli extension. In this guide, we'll explore the context of the problem and provide a step-by-step solution to ensure your code runs smoothly.

The Problem

Consider a scenario where you are fetching rows from a MySQL database and displaying data on your page. The retrieval works as expected in one instance, but throws an error in another. Here’s a simplified view of the situation:

You use a prepared statement to retrieve data from your MySQL database.

The first instance of echo works perfectly, but the second one produces a Customizable_Exception error, indicating that you're trying to access a property of a non-object.

Example Code That Causes the Error

[[See Video to Reveal this Text or Code Snippet]]

In the above code, the first echo executes within the loop, successfully fetching and displaying data. However, when the loop ends, $row_feed no longer holds a valid object, leading to the error when trying to access it outside the loop.

The Root Cause: Loop Behavior in PHP

The problem lies in the behavior of the fetch_object() function used within a loop. Here's how it works:

Inside the while loop, fetch_object() will return NULL when there are no more records to read, causing the loop to terminate.

Once the loop ends, the $row_feed variable does not retain the last fetched object; it becomes NULL.

Key Point

After the loop, attempting to access properties of $row_feed will yield an error since it no longer refers to a valid object.

Solution: Preserve Last Fetched Value

To resolve this issue, you can store the last fetched object into a different variable inside the loop. This allows you to reference the last row after exiting the loop without encountering the non-object error.

Using a Variable to Store the Last Row

Here’s how to modify the code:

[[See Video to Reveal this Text or Code Snippet]]

Summary of the Solution

Initialize a new variable: Before entering the loop, create a variable (e.g., $last_row) to store the last fetched object.

Update the new variable inside the loop: Assign $last_row the value of $row_feed during each iteration of the loop. This way, it retains the last valid object after the loop terminates.

Safely access the last object: After the loop, check if $last_row is not NULL before trying to access its properties, ensuring you avoid any non-object errors.

Conclusion

By following the steps outlined above, you can effectively handle the Trying to get property of non-object error when dealing with multiple instances of data retrieval in your PHP application. This approach not only makes your code more robust but also enhances its clarity and maintainability. Always remember to check the state of your variables after control structures like loops to prevent unexpected errors.

Happy coding!