PHP function Exercises: Reverse a string

Last update on December 20 2024 10:19:09 (UTC/GMT +8 hours)

Write a PHP function to reverse a string.

Visual Presentation:

PHP function Exercises: Reverse a string

Sample Salution:

PHP Code:

<?php
// Function to reverse a string recursively
function reverse_string($str1)
{
    // Get the length of the string
    $n = strlen($str1);
    
    // Base case: if the string has only one character, return the string itself
    if ($n == 1)
    {
        return $str1;
    }
    else
    {
        // Decrement the length of the string
        $n--;
        
        // Recursively reverse the substring starting from the second character
        // and concatenate the first character to it
        return reverse_string(substr($str1, 1, $n)) . substr($str1, 0, 1);
    }
}

// Call the reverse_string function with the argument '1234' and print the result
print_r(reverse_string('1234') . "\n");
?>

Output:

Explanation:

In the exercise above,

The function "reverse_string()" takes a single parameter '$str1', representing the input string to be reversed.
It calculates the length of the input string using 'strlen($str1)' and stores it in the variable '$n'.
If the length of the string is 1, it means the string is already reversed, so it returns the string itself.
Otherwise, it decrements the length of the string by 1 ($n--), and then recursively reverses the substring starting from the second character using 'substr($str1, 1, $n)', and concatenates the first character using 'substr($str1, 0, 1)'.
This recursive process continues until the base case (string length equals 1) is reached, and the reversed string is gradually built up.
Finally, the function is called with the argument '1234', and the reversed string is printed using "print_r()" function.

Flowchart :

PHP Code Editor:

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