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PHP Exercises: Exchange the first and last characters in a given string and return the new string


7. Exchange First and Last Characters

Write a PHP program to exchange the first and last characters in a given string and return the new string.

Sample Solution:

PHP Code :

<?php
// Define a function named "test" that takes a parameter $str
function test($str) 
{
    // Use a ternary operator to check if the length of $str is greater than 1
    // If true, concatenate the last character with the substring from index 1 to length-2
    // and then concatenate the first character at the end
    // If false, return $str as it is
    return strlen($str) > 1 ? substr($str, strlen($str) - 1) . substr($str, 1, strlen($str) - 2) . substr($str, 0, 1) : $str;
}

// Call the test function with argument "abcd" and echo the result
echo test("abcd") . "\n";

// Call the test function with argument "a" and echo the result
echo test("a") . "\n";

// Call the test function with argument "xy" and echo the result
echo test("xy") . "\n";
?>

Explanation:

  • Function Definition:
    • The function test takes one parameter, $str.
  • Conditional Check:
    • It uses a ternary operator to check if the length of $str is greater than 1.
    • If true:
      • Constructs a new string by:
        • Taking the last character of $str using substr($str, strlen($str) - 1).
        • Appending the substring from index 1 to the second-last character with substr($str, 1, strlen($str) - 2).
        • Adding the first character at the end using substr($str, 0, 1).
      • This effectively swaps the first and last characters of $str.
    • If false:
      • Returns $str as is (for strings of length 1 or less).
  • Function Calls and Output:
    • First Call: test("abcd")
      • Swaps the first ("a") and last ("d") characters, resulting in "dbca".
    • Second Call: test("a")
      • Returns "a" since the length is 1.
    • Third Call: test("xy")
      • Swaps "x" and "y", resulting in "yx".

Output:

dbca
a
yx

Visual Presentation:

PHP Basic Algorithm Exercises: Remove the character in a given position of a given string.

Flowchart:

Flowchart: Remove the character in a given position of a given string.

For more Practice: Solve these Related Problems:

  • Write a PHP function to swap the first and last characters of a string, accounting for strings with one or two characters.
  • Write a PHP script to exchange the first and last letters using substring extraction without built-in reversal functions.
  • Write a PHP program to perform character swapping on a string and handle cases where the string is empty or one-character long.
  • Write a PHP script to swap the initial and final characters and test with various string lengths using manual indexing.

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