<?php
$handle = fopen("input.txt", "r");
$gArr = array();
if ($handle) {
    while (($line = fgets($handle)) !== false) {
        $lineArr = explode(" ", $line);
        $lineArr = array_map('trim', $lineArr);

        if(array_key_exists($lineArr[0],$gArr)== false){
            $gArr[$lineArr[0]] = array_fill(1, 5, 0);
        }
        if(array_key_exists($lineArr[1], $gArr) == false){
            $gArr[$lineArr[1]] = array_fill(1, 5, 0);
        }
        $gArr[$lineArr[0]][$lineArr[1]] = (int)$lineArr[2];
        $gArr[$lineArr[1]][$lineArr[0]] = (int)$lineArr[2];
    }
    fclose($handle);
} else {
    // error opening the file.
}
var_dump($gArr);