gistfile1.php

<?php

////////////////////////////////////
// This is my answer to the following
// http://skilleo.me/challenge/2
//
//
// Seems to crash it out =/
////////////////////////////////////

function pairOfCharacters($a) {
    /* Create the code to find the pair of characters here. */
	    /* Create the code to find the pair of characters here. */
    $tmp = array();
	foreach($a as $char) {
		$tmp[$char] = (isset($tmp[$char]) ? $tmp[$char]++ : 1);
	}
	
	foreach($tmp as $key => $val) {
		if($val > 1) { echo $key."\n"; }	
	}
    
}

$__fp = fopen("php://stdin", "r");
$_a = fgets($__fp);
$_a = explode(' ',$_a);
$res = pairOfCharacters($_a);
echo $res;

?>