What are the potential pitfalls of using single quotes for variable interpolation in PHP session variable names?

Using single quotes for variable interpolation in PHP session variable names can lead to the variable name being interpreted as a literal string, rather than as a variable. This can result in errors or unexpected behavior in your code. To avoid this issue, it's recommended to use double quotes for variable interpolation in PHP session variable names.

// Incorrect usage of single quotes for variable interpolation in session variable names
$_SESSION['user_$id'] = 'John Doe';

// Corrected usage of double quotes for variable interpolation in session variable names
$_SESSION["user_$id"] = 'John Doe';