PHP Program to Print All Duplicate Characters in a String

This article will show you how to print duplicate characters in a string using PHP. Detecting and printing duplicate characters in a string is a common task in programming. In this article, we will explore various approaches to achieve this.

Using array_count_values() Function

The array_count_values() function is used to count the occurrences of each value in an array, simplifying the process.

PHP

<?php

function printDuplicates($str) {
    $charCount = array_count_values(str_split($str));

    // Print duplicate characters
    echo "Duplicate characters: ";
    foreach ($charCount as $char => $count) {
        if ($count > 1) {
            echo "$char ";
        }
    }
}

// Driver code
$str = "Welcome to GeeksforGeeks";

printDuplicates($str);

?>

Output

Duplicate characters: e o   G k s 

Using Associative Array

One of the most basic methods is to use an associative array to keep track of the occurrence of each character in the string.

PHP

<?php

function printDuplicates($str) {
    $charCount = [];

    // Iterate through each character
    // in the string
    for ($i = 0; $i < strlen($str); $i++) {
        $char = $str[$i];

        // Check if the character is already
        // in the associative array
        if (isset($charCount[$char])) {
            $charCount[$char]++;
        } else {
            $charCount[$char] = 1;
        }
    }

    // Print duplicate characters
    echo "Duplicate characters: ";
    foreach ($charCount as $char => $count) {
        if ($count > 1) {
            echo "$char ";
        }
    }
}

// Driver code
$str = "Welcome to GeeksforGeeks";
printDuplicates($str);

?>

Output

Duplicate characters: e o   G k s