In Python, the def keyword is used to define and create a new function. This statement is followed by the function name and a block of code that defines the function's behavior.

The __name__ variable in Python is used to determine if a Python script is being run as the main program (__name__ is set to "__main__") or if it is being imported as a module into another script (__name__ is set to the name of the module). This allows you to create reusable modules that can also be run as standalone scripts.

You can execute a Python file from within another Python file using subprocess.call('file.py', shell=True) to run it as a separate process. The other options are not used for running external Python files.

To dynamically import a module when you have the module's name stored in a string variable, you would use:

import(moduleName)

However, this isn't directly valid syntax in Python.

The recommended way for Python 2.7 and 3.1 and later is to use importlib module:

import importlib
module = importlib.import_module(moduleName)

With Python older than 2.7/3.1, using __import__ you can import a list of modules by doing this:

>>> moduleNames = ['sys', 'os', 're', 'unittest']
>>> moduleNames
['sys', 'os', 're', 'unittest']
>>> modules = map(__import__, moduleNames)

To remove duplicate values from a list in Python, you can convert the list to a set. Sets automatically store only unique values, so when you convert a list to a set and back to a list, duplicates are removed. The other options do not directly address the removal of duplicates.

To handle an exception for an error caused by dividing by zero in Python, you should use a try-except block. Inside the try block, you should place the code that might raise the exception, and in the except block, you can define how to handle the exception gracefully. The other options are not suitable for handling this specific exception.

The non-scalar data type in PHP is an array. Arrays can hold multiple values and are not considered scalar because they are collections of values, not single values. Scalars include integers, strings, and booleans.

To check the data type of a variable in PHP, you use the gettype() function. This function returns a string indicating the data type of the variable, such as "integer," "string," or "array."

Magic constants in PHP are predefined constants, such as __FILE__, __DIR__, and __FUNCTION__, which provide information about the code's context. __VARIABLE__ is not a valid magic constant.

In PHP, the strlen() function is used to determine the length (number of characters) of a string. It's particularly useful for validating input or working with text data.

Constants in PHP are defined using the define function. It's not a keyword but a function used to create named constants with a specific value.

PHP is loosely typed, meaning that data types are dynamically determined by the context in which they are used. Variables can change their data type as needed.