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Queries are one of the most used items out of all of the interfacing we will want to do with our PDO object. Let's take a closer look at queries using PDO and what these queries will return to us.
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Queries, are one of the most used items,
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out of all of the interfacing we'll want
to do with our PDO object.
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Let's take a closer look at queries, using
PDO and
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what these queries will return to us.
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The time has now come for us to query our
database and
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get a set of films, that return back to us
directly from the database and
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we'll store it into a variable.
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The way that we're gonna do that is by
running a method that is built in to
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the PDO object.
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So let's take a look at the docs again for
the PDO class.
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We'll just go and open up a new tab.
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Pdo, php, and the first one should be the
pdo manual.
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That's good.
And this is the introduction.
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We're just gonna scroll down here and
click, directly on the pdo class.
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Okay, scroll down.
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Take a look at the methods.
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The one that we're gonna want,
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is over here on the right, about three
quarters of the way down, called query.
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So, it's a public, it will return a pdo
statement, and
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it is query, is the method name.
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And then the single argument is a string,
or the SQL statement that you wanna run.
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You click on the query link, it'll say
just the same,
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it executes a SQL statement, returning
a result set as a PDOStatement object.
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So it's gonna return to us a new object
called a PDOStatement.
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So let's start, by coming over here and
running our query on the db object.
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So, we can do that right here in our
index.php file.
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Let's go ahead and clean up our file a
little bit so
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that we only have the information that we
need in that file.
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So for instance, on the index page, we're
gonna wanna this database connection, but
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we might want that connection on other
pages, as well.
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So we'll create a new file, called
database.php.
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And so let's do a new file, database.php.
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Open up that file and
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we're gonna actually copy the information
from this first section.
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I'm actually just gonna cut it all the way
out.
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All right, save our index file, and I'm
gonna paste this in.
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So, this is still setting our errors to
on, we still want that for now.
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It's gonna be our try-catch block it's
gonna have a db object here on line seven,
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and at the very end of this file, the db
object will still exist.
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The key here, is that we want to include,
or in our case, called require,
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require this file to be present inside of
the index.php file.
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So, let's open up our php tags again,
we'll close them out.
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And then, we'll keep just the code
specific to this index file in here.
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We'll do that by using the internal
function require_once and
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then require once, needs a file name,
which is for us is gonna be database.php.
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All right, close that out.
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And now we have required that the database
file be there.
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The way we can make sure that it's
requiring the file, that it's including
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the file inside the index dot PHP is to
now var_dump and die our actual DB object.
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So let's do that just as an example.
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Dollar sign db as our object or our pdo
object, and
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then we're on the statement die and that
will stop the process.
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So, we'll close this manual out and we'll
go here and hit our preview icon.
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And now you'll see that we are dumping and
dieing our PDO object.
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But this time our database file is
separately included or
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required into our index file.
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So, now that we don't need this code any
longer, I'm gonna actually close it out.
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And we'll continue running our query from
here at the index.php file.
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So let's remove lines 5 and 6, and then
I'm going to create a new
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connection to the database, or rather a
new method to the database, called query.
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And we're gonna do that by doing $db and
then the object operator to query.
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Open and close our parenthesis and close
it out with a semicolon.
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Now if you recall from the documentation
it takes a single string.
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So in our case our single string is going
to be for this particular page.
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Select * from film.
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So we're taking and just grabbing
everything.
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Not very efficient at the moment, but
let's just, just for
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an example, we'll do select, star, film.
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Okay.
Now that is our query.
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Now, it returns to us an object.
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So, we actually need to store this
somewhere.
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So I'm gonna call it results.
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All right.
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And then on the next line, let's dump it
and
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see what the results object looks like.
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So what we'll do, var_dump and then pass
the results.
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Close it out.
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And then die at the next statement, or the
next line.
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Save our file, and then go back and hit
preview again.
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So here we'll see our object, the
PDOStatement object, and
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then it says there is one item in there,
and
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that is the query string, which is select
star from film.
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That's great but, it's really not giving
us a whole lot of information so
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we're gonna actually need to work with
this result set, more in detail and
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we also need to manage our errors because
let's say for instance our query string is
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wrong and we just say like D from film,
which would not be correct.
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And then we go back and refresh, we have
an uncaught exception.
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And like we learned earlier, we don't want
uncaught exceptions in our code.
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So we need to wrap this in a try and
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catch block we'll do that next and work
with the result set.
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