Sorting with headers

<?php
$animals = file('https://gist.githubusercontent.com/atduskgreg/3cf8ef48cb0d29cf151bedad81553a54/raw/82f142562cf50b0f6fb8010f890b2f934093553e/animals.txt', FILE_SKIP_EMPTY_LINES);
sort($animals);

$last = '';
foreach ($animals as $animal) {
    $current = substr($animal, 0 ,1);
    if($current !== $last) {
        echo $current, ' ---<br>', PHP_EOL;
        $last = $current;
    }
    echo $animal;
}