Editing relationships

The tables

Here are the tables for the goat app:

Users are going to use a form to record each goat's fave comedian. Like this:

How will that work?

The HTML

Let's check out the HTML that we'll need to generate.

select doesn't have the multiple attribute, so users can only choose one comedian.

Each option has the name of a comedian, and that comedian's id. For example:

Roisin (pronounced Ro-sheenn) is record 4.

When editing a goat's data, the goat might already have a fave comedian set. We want to make sure that comedian is selected when the form first displays. You do that with the selected property:

PHP for the form

We want PHP that...

• Makes an option tag for every comedian in the DB.
• Adds the selected property to the one that is the goat's current fave.

goat-add-edit.php is the page with the form. It has this on it:

I made functiony friends to make widgets. The middle widget is the one we're going to talk about, the one for the fave comedian.

Actually, I didn't put these friends in a library. I put them at the end of goat-add-edit.php, the page that makes the form.

That's one reason to make functions, but not the only one. Separating code into functions also makes code easier to write. When I was writing goat-add-edit.php, I just put in the call to the function...

When I was writing that code, I thought to myself:

Self, don't worry about the function's deets for now.

That reduced the load on my brain.

Later, I wrote the function. When doing that, I didn't have to think about the rest of the page. I could focus just on the function.

Keeping the load on your brain under control is very important in programming. Functiony friends help you with that.

Here's the code for making the dropdown (the select) for the fave comedian. Remember, we want to make this HTML:

The PHP:

You send in two values:

• The id of current fave. If there isn't one, it will be null.
• The records for all of the comedians.

Lines 8-11 make HTML for the start of the widget. It will be the same always, for every goat, and as comedians are added and removed.

Lines 12-20 are repeated for every comedian. Line 19 outputs the HTML:

Notice the variable $selected is output every time through the loop. It's set to MT towards the start of the loop (line 15):

Then, if the comedian the loop is processing, is the fave, $selected is changed.

Processing fave comedian

The form sends the data to another page, through the session:

Before sending the data, though, the form page does a little processing.

Remember that getParamFromPost() returns null if it can't find a value for the param fave-comedian. But there's another case that might cause problems. What if the user select the first option?

Here's the HTML for that option:

The value is 0. No comedian has 0 for their id. When we do...

... $goatFaveComedianId will be incorrect.

So, let's add an if to take care of that:

If the user doesn't touch the dropdown, or if they select the first option, $goatFaveComedianId will be null.

Saving

goat-save.php picks it the user's choice, a comedian id, or null.

Then inject the value into SQL, e.g.:

Recall that null is what MySQL uses for an MT field. We've already made sure that, if the user does not choose a comedian, $goatFaveComedianId will be null.

Clubs

Looking further down the form made by goat-add-edit.php, we see another dropdown for club membership:

Here's the HTML that made it:

There's the multiple property in line 2, along with [] at the end of the name. That means the processing page will get an array for this widget, which we need if users are to select more than one element.

You can see that clubs 1 and 5 are selected.

More PHP

To make the widget, we need to know two things:

• Which clubs the goat is in.
• The names and ids of all the club.

This function will find the clubs a goat is in.

Pass it a goat id, and it will return an array of the clubs. It returns all of the data about the clubs, rather than just their ids.

So, to make the widget, we need to know two things:

• Which clubs the goat is in. >>DONE<<
• The names and ids of all the club.

The second one is easier.

To make the widget, we need to know two things:

• Which clubs the goat is in. >>DONE<<
• The names and ids of all the club. >>DONE<<

Here's the first line of the function that makes the widget:

The first param is the clubs the goat is in. The second is all of the club data. Here's what the debugger says about the first param, $goatClubMemberships:

The goat is in two clubs, so there are two elements in the array. Each element gives the deets of a club:

The second param of...

... is $clubRows.

Aye! Good thinking, Adela.

Here's PHP to make the widget.

Line 9 has something new:

Remember that $goatClubMemberships is an array of arrays:

There's one element in $goatClubMemberships for each club. Each of those elements has an element called club_id. Every club has to have an id, so the ids will be there for every record.

...extracts the club_ids for every element in $goatClubMemberships, and returns an array of them. Here's what the debugger sees:

So, $memberOfClubIds is an array of the ids the goat is a member of. That comes in handy later in the function.

Here's the loop that makes the option tags.

The loop runs across $clubRows. That's an array of all of the clubs. So the code in the loop is run for every club. Each time through the loop, $clubRow is the deets for one club.

By line 18, $clubId has the id of the club being processed. Line 18 is:

in_array() returns true of the $clubId is in the array $memberOfClubIds. That's the ids of the clubs the goat is in, that we made earlier with array_column().

Aye, it is.