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As you might have noticed by now that engine X configuration syntax closely resembles that of a programming

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language implementing in some ways the concept of scope includes and in this lesson in variables and

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conditionals variables exist in two forms variables.

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We set ourselves and engine exis own built in variables we can find a list of these engine X variables

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in the engine X dot org documentation alphabetical index of variables which lists each of the available

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variables with the module that makes it available modules like hgt underscore core and h.t. dp log.

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Really being part of engine X so you don't have to manually add them.

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Now these native variables can be extremely useful.

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So let's switch back to that configuration file and see how we could use them.

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I'll clear all of these locations from the previous lesson create a new location for Slash inspect.

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And in this location simply return a few of these.

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Engine X variables return status 200 a string and using double quotation marks.

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We can directly embed variables into this response string.

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First one I'll add is the host variable variables being prefixed with a dollar sign.

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Add a new line character.

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You are a new line and ARGs which is the requests query string save this and reload the configuration.

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Navigate to that new location.

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Slash inspect.

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And we see each variable on its own line.

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The host which is the server I see as I'm not using the domain name and the request.

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You are I slash inspect.

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Of course we didn't pass a query string so the args variable is empty.

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But if I add query name equals Ray that's now also returned albeit in its complete string form.

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We can however use a variation of the args variable to get individual query parameters.

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I'll change this string to name.

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Argh underscore name.

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So based on the query string engine it compiles a named variable for each parameter prefixed with Arg

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save and reload this.

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Reload and this time we get the value of the name parameter.

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So already a very powerful feature set of engine X engine X also allows us to perform basic conditionals

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or if statements which most commonly will be used in conjunction with one of these variables before

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I demonstrate however.

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Note that the use of engine X conditionals inside location contexts is highly discouraged as this can

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lead to some very unexpected behaviour.

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Now the technicalities of this is beyond the scope of what we can cover here but if you'd like to read

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more on the subject I've linked to a very detailed explanation in the list and resources.

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Righto.

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Outside of this location context then I'll create a conditional which for the sake of demonstrating

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chicks are hypothetical AP Iki if with braces.

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Note the space between the F and the braces being required for this syntex to be valid.

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Argh underscore a p Iki.

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So checking the value of the API key query parameter not equal to 1 2 3 4.

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Meaning if the user does not pass the value 1 2 3 4 as the API key parameter in the query string to

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any you are a return of foro 1 which is the unauthorized status code.

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Incorrect API key.

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Save this.

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Reload with alt that API parameter key this time just requesting the root.

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You are right.

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So their demo site and we're denied.

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As per that conditional add the API key parameter.

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However with a value of 1 2 3 4 and were served indexed update the amelle as the conditional did not

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evaluate to true image and style sheet simply being missing as the internal requests for those didn't

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include the API key parameter.

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OK as I mentioned we can also set our own variables within range and X configuration.

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I'll get rid of all this and to create a new variable we can say set the variable name.

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I'll make this weekend and the variable value.

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No so no equals sign.

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Just the standard engine X director format variables can be set to simple strings such as this example

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integers or booleans.

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True and false then for another hypothetical use case we can check if it is weakened by creating an

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if statement and using the date underscore local engine x variable.

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This variable holding an ISO date time string for the local time and instead of a simple equals or not

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equals operator.

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We can use a regular expression as with location contexts folder checking on this variable for Saturday

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or Sunday.

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In which case if this is true set weekend 2 Yes.

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So starting out we said weekend to be No.

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Check the local date to see if it is in fact Saturday or Sunday which if it is we changed the value

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of weekend to be yes.

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Change this location to is WEEKEND.

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Returning two hundred and the weekend variable.

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So yes or no.

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Save and reload the configuration.

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Navigate to that you are I is under school weekend and it being a Monday at the time of recording this

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we get no.

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Change the condition to check for Monday instead then.

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I'll rename this variable to mun.

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And said the location to is Monday.

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Reload.

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Navigate to is Monday.

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And this time we get yes as this conditional evaluator.

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True true and updated the variable to be yes in the next place and we'll use some of these variables

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to learn about rewrites and redirects.