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

Last update on December 20 2024 10:20:32 (UTC/GMT +8 hours)

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:

Flowchart:

PHP Code Editor:

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Next: Write a PHP program to create a new string which is 4 copies of the 2 front characters of a given string. If the given string length is less than 2 return the original string.