In PHP function calls, how do you pass a variable by value rather than by reference?

Introduction / Context:
Understanding how PHP passes arguments to functions is an important foundation topic. PHP supports both pass by value and pass by reference, but the default behaviour is pass by value. This question checks whether you know that you do not need any special syntax to pass by value and that reference passing is the special case that uses an ampersand.

Given Data / Assumptions:

• We are working with user defined functions in PHP.
• The developer wants changes inside the function not to affect the original variable outside the function.
• There is a basic understanding that PHP supports references using ampersands.

Concept / Approach:
In PHP, function parameters are passed by value unless explicitly marked otherwise. This means that the function receives a copy of the value, and assignments to the parameter inside the function do not change the original variable. To pass by reference, both the function parameter definition and sometimes the call (in older styles) use the ampersand &. Therefore, to pass by value you simply avoid using & in the parameter list and the call, relying on the default behaviour.

Step-by-Step Solution:
Step 1: Recall that a typical PHP function definition might look like function demo($x) { }.Step 2: In this form, $x receives a copy of the argument value when demo() is called, which is pass by value.Step 3: If you wanted pass by reference, you would write function demo(&$x) { }, which clearly uses an ampersand.Step 4: Since the question asks how to pass by value, the correct answer is to use the normal form without the ampersand.Step 5: Option A states exactly this default behaviour and is therefore correct.

Verification / Alternative check:
You can test this with a simple script. Define function change($num) { $num = $num + 10; } and then call $a = 5; change($a); echo $a; The output remains 5, confirming that $a was not modified. If you change the function to function change(&$num) and call it again, $a becomes 15. This experiment confirms the default pass by value behaviour.

Why Other Options Are Wrong:
Option B reverses the role of the ampersand and incorrectly claims that & is needed to pass by value. Option C denies the existence of pass by value, which contradicts both documentation and everyday usage. Option D claims that converting to a string is required, which has nothing to do with argument passing semantics.

Common Pitfalls:
Developers sometimes use references too aggressively and end up with confusing side effects, especially when dealing with arrays. Another pitfall is believing that objects are always passed by value in the same way as scalars; in modern PHP, object variables behave more like references to the same underlying object. It is important to understand both value and reference passing rules clearly to avoid unintentional modifications.

Final Answer:
By default PHP passes arguments by value, so you simply declare the parameter without an ampersand and call the function normally to pass by value.