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Using isset or is not set with variable in PHP?

Hey there fellow developers,

I've been working on a PHP project and I came across a situation where I need to check if a variable is set or not. Now, I'm a little confused about which approach to use: isset or is not set. I understand that both can be used to achieve the same result, but I'm not sure which one would be the best practice or more appropriate in this scenario.

To provide some context, let me explain the specific situation I'm dealing with. I have a form where users can enter some data, and I'm storing that data in variables to be used later on. However, not all form fields are required, so some variables might not be set depending on what the user fills out.

In my case, I want to check if a specific variable has been set before using it further down in my code. But I want to do it in a way that is considered best practice and follows the PHP coding standards.

So, my question is: should I use isset or is not set to check if a variable is set or not? And which one would be recommended in this scenario? I would really appreciate it if someone could shed some light on this confusion and provide some guidance.

Thanks in advance for your help!

All Replies


Hey there,

In my personal experience, when it comes to checking if a variable is set or not in PHP, I usually prefer using `isset()`. The `isset()` function is specifically designed for this purpose and it returns true if the variable exists and has a non-null value.

One advantage of using `isset()` is that it can check multiple variables at once, making it quite handy when you have a lot of variables to validate. Additionally, `isset()` is a language construct, so it has better performance compared to other approaches like `is not set`.

Another benefit of using `isset()` is that it won't throw a notice if the variable doesn't exist. This is particularly useful when you're dealing with user input or external data, where certain fields may or may not be present.

However, please keep in mind that if you use `isset()` on an array element that has a `null` value, it will return false. So, if you anticipate the possibility of having `null` values, you might need to handle that separately.

Overall, in my opinion, `isset()` is a reliable and widely used method for checking variable existence in PHP. It keeps the code clean and readable while efficiently handling the checking operation. Hope this helps!


Hey everyone,

From my personal experience, when it comes to checking if a variable is set or not in PHP, I have found the "is not set" approach to be more suitable in certain situations.

Instead of using the traditional `isset()` function, I prefer using the negation (`!isset()`) to determine if a variable has not been set. I find this to be particularly useful when I want to explicitly check if a variable is not set, rather than just determining if it is set. This approach helps me express my intention more clearly in the code.

Additionally, using `!isset()` allows me to combine it with other conditions without the need to nest another `if` statement. For example, if I want to check if a variable is not set and also validate another condition, I can simply use `!isset() && condition`. This can make the code structure cleaner and more concise.

However, it's important to note that relying solely on the "is not set" approach may have its drawbacks. Unlike `isset()`, `!isset()` can trigger a warning if the variable does not exist. Therefore, it's crucial to ensure that the variable you are checking genuinely exists or consider using error suppression techniques.

To summarize, while both `isset()` and the "is not set" approach can achieve similar results, I tend to lean towards the latter when I want to explicitly check if a variable is not set, and when I can benefit from combining conditions in a concise manner. Nevertheless, it's crucial to be cautious and handle any potential warnings that may arise.

Hope this sheds some light on an alternative approach to checking variable existence in PHP!

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