Write a PHP program to create a new string from a given string without the first and last character if the first or last characters are 'a' otherwise return the original given string

<?php
function test($s1)
 { 
    if (strlen($s1) > 0 && substr($s1, strlen($s1)-1, 1) == "a")
            {
                $s1 = substr($s1, 0, strlen($s1) - 1);
                
            }

    if (strlen($s1) > 0 && substr($s1, 0, 1) == "a")
            {
                $s1 = substr($s1, 1);
       
            }

            return $s1;
     }    
 

echo test("abcab") . "\n";
echo test("Python") . "\n";
echo test("abcda") . "\n";
echo test("jython") . "\n";