1. array_map()

Purpose: Applies a callback function to each element of one or more arrays and returns a new array with the results.

Key Points:
Returns a new array.
Does not modify the original array.
Can work with multiple arrays in parallel.

2. array_filter()

Purpose: Filters an array using a callback function — keeps only the values for which the callback returns true.

Key Points:
Returns a new filtered array.
Does not modify the original array.
Removes elements that don’t match the condition.

3. array_walk()

Key Points:

Modifies the original array.
Does not return anything useful (returns true on success).
Cannot change keys.

Purpose: Applies a callback function to each element of the array by reference. Mostly used for modifying the array in place.

Summary: