Why am I getting a 'A non well formed numeric value encountered' error when using PHP's `date()` function with a GET parameter?

Understanding "A non well formed numeric value encountered" Error in PHP

When attempting to validate dates passed from a form, you may encounter the error "A non well formed numeric value encountered." This error indicates that you're trying to use a value that's not a well-formed number.

In your specific case, you're getting this error while trying to use the date() function with a GET parameter representing a start date. The issue arises because this parameter is being passed as a string in the format "2020-10-10" or "2020/10/10," which is not a valid numeric value for the date() function.

Resolving the Issue

To resolve this issue, you need to convert the date parameter to a numeric value before passing it to the date() function. You can use the strtotime() function to convert the string date representation to a number of seconds. Here's the corrected code:

date("d", strtotime($_GET['start_date']));

Additional Considerations

It's crucial to understand the root cause of this error type. Whenever you encounter such an error, you should first investigate the problem value using var_dump(). This will help you determine the following:

• If you're accessing an incorrect variable or data structure.
• If the value can be converted to a valid numeric format (e.g., using strtotime()).
• If the source of the problem data requires validation or logic adjustments.

Never resort to blindly casting the problem value to a number, as this will conceal the actual problem and potentially lead to incorrect results.

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