In PHP, which of the following groups contains only built-in functions that are specifically used for sorting arrays?

Introduction / Context:
PHP arrays are very flexible and support many operations, including sorting by values or keys in ascending or descending order. PHP provides a family of dedicated sorting functions, such as sort(), rsort(), asort(), arsort(), ksort(), and others. Knowing which functions are specifically designed for sorting arrays is important for writing correct and readable PHP code and is a common interview topic for PHP developers.

Given Data / Assumptions:

• We are using PHP associative or indexed arrays.
• We want to sort arrays either by value or by key.
• PHP has separate built in functions for sorting rather than relying on generic utility functions.
• The question asks us to identify the group that contains only array sorting functions.

Concept / Approach:
PHP's sorting functions include sort() and rsort() for sorting values of indexed arrays, asort() and arsort() for sorting values while preserving keys, and ksort() and krsort() for sorting by keys. There are also user defined sort variants like usort(), uksort(), and uasort() that accept custom comparison callbacks. To answer this question, we must pick the option where every function listed is part of this sorting family, and none of the listed functions perform unrelated tasks like file handling, array push/pop, or string concatenation.

Step-by-Step Solution:
Step 1: Examine option A: sort(), rsort(), asort(), ksort(). All four are standard PHP functions used for sorting arrays: sort and rsort for values, asort for value sort preserving keys, and ksort for key sorting. Step 2: Examine option B: array_push(), array_pop(), sort(), echo(). array_push and array_pop manipulate array elements at the end, and echo outputs strings; only sort() is a sorting function, so this group is mixed and incorrect. Step 3: Examine option C: ksort(), fopen(), fclose(), rsort(). fopen and fclose are file handling functions, not sorting functions, making this option invalid. Step 4: Examine option D: implode(), explode(), print(), asort(). implode and explode handle string and array conversions, and print outputs text; only asort() is a sorting function, so this set is also mixed. Step 5: Conclude that option A is the only group where all entries are dedicated array sorting functions.

Verification / Alternative check:
You can verify these behaviours with a simple PHP script. Applying sort(), rsort(), asort(), and ksort() to arrays clearly changes the order of elements based on values or keys. Consulting the PHP manual confirms that each of these functions belongs to the array sorting function family. By contrast, functions like array_push(), fopen(), or implode() are documented under array manipulation, filesystem, or string handling categories and not under sorting, confirming that option A is correct.

Why Other Options Are Wrong:
Option B is wrong because array_push() and array_pop() only add or remove elements at the end of an array, and echo() is used for output, not sorting. Option C is incorrect because fopen() and fclose() work with files, not arrays. Option D is wrong because implode() and explode() convert between strings and arrays, while print() outputs text; only asort() in that set is a sorting function.

Common Pitfalls:
A common pitfall is using sort() on associative arrays and expecting keys to be preserved; sort() reindexes numeric keys, so asort() or ksort() are more suitable when keys matter. Another mistake is confusing user sort functions like usort() with standard sorts and forgetting to provide the necessary callback. Developers should choose the sort function that matches the desired behaviour: by value or by key, ascending or descending, and whether keys should be preserved.

Final Answer:
The group that contains only PHP array sorting functions is sort(), rsort(), asort(), ksort().