Class as a Set of Methods in OOP in PHP

Sometimes classes are used to group methods of similar topics. In this case, as a rule, only one object of this class is created and its methods are used many times in various situations.

Let's look at an example. Let's create a class that will manipulate arrays of numbers:

<?php
	class ArrHelper {
		
	}
?>

Each method of this class will take an array as a parameter and perform a specified operation on it. Let's say, for example, we have the following methods:

<?php
	class ArrHelper {
		public function getSum($arr) {
			// sum of elements
		}
		
		public function getAvg($arr) {
			// arithmetic mean
		}
	}
?>

Let's write the implementation of these methods:

<?php
	class ArrHelper {
		public function getSum($arr) {
			$res = 0;
			
			foreach ($arr as $num) {
				$res += $num;
			}
			
			return $res;
		}
		
		public function getAvg($arr) {
			$len = count($arr);
			
			if ($len > 0) {
				$sum = $this->getSum($arr);
				return $sum / $len;
			} else {
				return 0;
			}
		}
	}
?>

Let's see how we will use these methods. Let's create an object of our class:

<?php
	$arrHelper = new ArrHelper();
?>

Let's find the sum of numbers of various arrays using our object:

<?php
	$sum1 = $arrHelper->getSum([1, 2, 3]);
	var_dump($sum1);
	
	$sum2 = $arrHelper->getSum([3, 4, 5]);
	var_dump($sum2);
?>

Make a Validator class, which will perform string validation for correctness.

Make a method in your class isEmail, checking if the string is a valid email.

Make a method in your class isDomain, checking if the string is a valid domain name.

Make a method in your class isNumber, checking if the string contains only numbers.