PHP Program to create comma delimited string from an array without using library function

<?php
//PHP code to reverse the string without 
//using library function

//function definition 
//it accepts an array and returns comma delimited string
function create_string($arr){
    //variable to store the string
    $str = '';
    
    for($i = 0; $i < count($arr); $i++){
        $str .= $arr[$i];
        if($i < (count($arr) -1)){
          $str .= ", ";
        }
    }
    
    //return the result i.e. comma delimited string
    return $str;
    
}

//main code i.e. function calling
$arr = array("New Delhi","Mumbai","Chennai","Banglore");
$result = create_string($arr);
echo "array is: ". "<br/>";
print_r($arr);
echo "comma delimited string: " .$result ."<br/>";

$arr = array("Google","Bing","Yahoo!","DuckDuckGo");
$result = create_string($arr);
echo "array is: ". "<br/>";
print_r($arr);
echo "comma delimited string: " .$result ."<br/>";
?>

Output

array is: 
Array
(
    [0] => New Delhi
    [1] => Mumbai
    [2] => Chennai
    [3] => Banglore
)
comma delimited string: New Delhi, Mumbai, Chennai, Banglore
array is: 
Array
(
    [0] => Google
    [1] => Bing
    [2] => Yahoo!
    [3] => DuckDuckGo
)
comma delimited string: Google, Bing, Yahoo!, DuckDuckGo