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session - Reserved characters in PHP $_SESSION variable keys

Hey everyone,

I have a question regarding the PHP $_SESSION variable keys and the reserved characters that can be used in them. I've been using PHP sessions in my web development project, and I want to make sure I have a clear understanding of what characters are allowed and what should be avoided when creating session variable keys.

From what I have gathered so far, the $_SESSION variable in PHP allows you to store information across multiple pages for a specific user session. The keys you use to access and set values in this superglobal array are essentially strings that identify the stored data.

However, I'm not sure if there are any reserved characters that I need to be careful of when naming my session variable keys. Can I use any symbol, number, or special characters in these keys, or are there specific characters that are not allowed or could potentially cause issues?

I want to ensure that I follow the best practices and avoid any conflicts or errors that might occur if I use reserved characters in my session variable keys. So, if anyone could shed some light on this topic and provide some guidance, I would greatly appreciate it.

Thank you in advance!

All Replies


Hey everyone,

As a developer who has been working with PHP sessions for some time now, I've encountered a few reserved characters when it comes to $_SESSION variable keys. I wanted to share my personal experience and shed some light on this topic.

While PHP allows you to use various characters in session variable keys, it's important to be cautious about using certain symbols that might cause conflicts or unexpected issues. One such character I came across is the dollar sign ($).

In PHP, the dollar sign has special significance as it denotes variables. If you use the dollar sign in a session variable key, it might lead to confusion or errors when accessing or manipulating the session data.

For instance, let's say you set a session variable with the key "$totalAmount", like this:

$_SESSION['$totalAmount'] = 100;

If you want to retrieve the value later, you might instinctively access it using the same key:

echo $_SESSION['$totalAmount'];

However, since PHP treats anything starting with a dollar sign as a variable, this will result in an undefined variable error. To correctly access the value, you would need to enclose the key in single or double quotes:

echo $_SESSION["$totalAmount"];

To avoid potential confusion or errors, it is prudent to avoid using symbols or special characters that have specific meanings in PHP, like dollar signs, percentage signs, and ampersands, as part of your session variable keys.

By sticking to letters, numbers, underscores, and hyphens, you can ensure clean and hassle-free session handling in your PHP code.

Feel free to share your own experiences or suggestions if you've come across any other reserved characters or best practices related to session variable keys.

Happy coding!


Hey there,

I've worked with PHP sessions quite extensively, and I can share my personal experience regarding reserved characters in $_SESSION variable keys.

In PHP, you can use any valid string as a session variable key. This means you can include letters (both uppercase and lowercase), numbers, and even special characters. However, it's important to note that there are a few characters that could potentially cause issues if used in session variable keys.

One such character is the dot (.) symbol. While it is not strictly a reserved character, it has a special meaning in PHP when used with arrays. PHP interprets dot-separated keys as nested arrays within the $_SESSION array. This can lead to unexpected behavior if you're not careful.

For example, if you set a session variable with the key "user.name" like this:

$_SESSION['user.name'] = "John Doe";

You'll end up with a nested array in the $_SESSION variable, where 'user' is an array containing a 'name' key. To access this value later, you'll need to use the array syntax:

echo $_SESSION['user']['name'];

So, to avoid any confusion or unexpected behavior, I'd recommend avoiding the dot symbol and any other characters that are commonly used as delimiters or have special meanings in PHP arrays. Stick to basic alphanumeric characters, underscores, and hyphens to ensure consistent and trouble-free usage of session variable keys.

I hope this helps clarify the issue for you. If anyone else has additional insights or experiences to share, please feel free to add to the discussion!


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