How can I check for a variable in Linux?

[isaacdarcilla]

Let the command to check if a Linux variable is existing is like this:

if [ -n "$MY_VARIABLE" ]; then
    echo "MY_VARIABLE is set to $MY_VARARIBLE"
else
    echo "MY_VARIABLE is not set"
fi

How can I achieve this in deploy.php?

[antonmedv]

Via https://www.php.net/manual/en/function.getenv.php