Easily update pocketmine! You can also choose the version to check out by doing ./update.sh <version>

update.sh

rm PocketMine-MP.phar.old 2> /dev/null
mv ./PocketMine-MP.phar ./PocketMine-MP.phar.old
echo "Backup of old Pocketmine-MP.phar stored at Pocketmine-MP.phar.old"
if [ $# -eq 0 ] # Empty arguments
then
    curl -s https://api.github.com/repos/pmmp/Pocketmine-MP/releases/latest \
      | grep "browser_download_url.*phar" \
      | cut -d : -f 2,3 \
      | tr -d \" \
      | wget -qi -
    echo "Updated to latest version!"
else # Specified version of pocketmine
    VERSION=$1
    URL="https://github.com/pmmp/PocketMine-MP/releases/download/$VERSION/PocketMine-MP.phar"
    if wget -q "$URL" > /dev/null;
      then
        echo "Version changed to $VERSION"
      else
        echo "Version not found!"
        echo "Reverting backup"
        mv Pocketmine-MP.phar.old Pocketmine-MP.phar 2> /dev/null
    fi
fi