interview.php

<?php

$host = 'palindromer-bd7e0fc867d57915.elb.us-east-1.amazonaws.com';
$port = 7777;

$socket = fsockopen($host, $port);

if (! $socket) {
    die('Error: connection not successful');
}

echo 'Processing lines ';

while ($line = fgets($socket)) {
    echo '.';

    // Divide the string into word chunks along spaces
    $words = explode(' ', $line);
    
    // Check for special line, denoting flag
    if (stripos($line, '!!!') === 0) {
        if (preg_match('/!!! flag\[(.*?)\]/i', $line, $matches)) {
            $response = $matches[1] . "\n";

            echo "\n\nFlag received: {$response}";
            fputs($socket, $response);

            return fclose($socket);
        }
    }
    
    // Get the palindromes
    $return = [];
    foreach ($words as $word) {
        if (isPalindromic($word)) {
            $return[] = $word;
        }
    }
    
    // Must respond with newline at the end
    $response = trim(implode(' ', $return)) . "\n";

    // Send response string
    fputs($socket, $response);
}

function isPalindromic($word)
{
    $word = trim($word);
    
    return $word == strrev($word);
}