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Managing Errors
8:17Managing errors in any application is very important, especially when it comes to database errors. We will manage this by wrapping our code that communicates with the database with a try catch block.
Managing errors in any application is very
important,
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especially when it comes to database
errors.
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We will manage this by wrapping our code
that communicates with
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the database within a try catch block.
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Continuing where we left off, we have
created our PDO object successfully.
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And then I demonstrated how we can break
that, so, we're gonna go ahead and
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break that again.
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So, I'm gonna add a few more A's back in
and
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see how we can handle these errors and
exceptions.
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Let's go ahead and refresh this.
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And now we'll see we have a fatal error,
uncaught exception.
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Well, we don't want that to happen.
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And if you recall from object-oriented
code practice.
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We have a lot of try-catch statements when
we're trying to catch exceptions and
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handle errors.
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So that's what we're gonna do, we're gonna
handle this PDL exception,
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by catching any general exceptions in our
script.
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So head back over to the index.php file.
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And then here we're gonna surround any
connection to the database.
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So here where we're creating our new
database,
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we're gonna actually surround that in a
try-block.
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So try, then open and close our curly
braces.
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Then we have a catch.
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Open and close parens.
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And then open and close our curly braces.
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Now, this is try catch block.
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Inside of here, we're gonna try any code
that we wanna run.
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And if it fails out or has an exception,
we want to catch that exception.
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So here we just simply put the class that
we want to catch,
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which is a PDO Exception, or we can use
the parent class to catch any exception.
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So, we'll type in Exception with a capital
E.
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And then the next argument is the actual
exception object that gets
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thrown when the error happens.
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So that one we'll just call it dollar sign
e for exception.
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Now we want to take this code here on line
11.
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In fact we'll do line 11, 12.
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We'll just copy it all.
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And we'll put it inside of our try block.
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So that way anything inside of
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here will happen only if the succesful
database object is created.
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So the other half of this coin here or the
other side of
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this coin is to actually put something in
here for our exception when that happens.
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So right now I'm just gonna echo a string.
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In that string let's say, sorry, the
connection was not successful.
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Okay?
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And then I also don't want it to continue
so I'll add another die statement here.
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[BLANK_AUDIO]
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Close it with a semicolon.
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Save our file.
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And I'm gonna refresh.
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So instead of it throwing an uncalled
exception, now it says,
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sorry the connection was not successful.
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Much cleaner, much nicer, no weird dumps
to the screen about our code.
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Exactly what we want.
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Now to make sure it works, we're gonna go
ahead and fix our error and then
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back in here, save our file, and then
let's redo our preview.
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And now we have our PDO object.
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Before we continue on we do want to do 2
more things to our try-catch block or
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to our PDO object and
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then our actual exception to make it a
little bit more informative for us.
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So let's go ahead over to a new tab and
let's open up the exception class.
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We're gonna go ahead and do that.
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I'm just gonna type in exception.php and
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here we have exception, which shows us the
actual exception class.
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If we scroll down here,
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we'll see that we have several different
methods that we can use.
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The one that we're going to want is
getMessage, which if we click on
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getMessage information it'll just say it
gets the exception message, and
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returns the exception message as a string.
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Head back over to your code, here I'm
going to modify line 11,
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I'm going to actually get rid of
everything there just to echo.
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I'm gonna pass through the actual
exception object.
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Just dollar sign e.
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And then an object operator.
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So that's a dash and a greater than
symbol.
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Looks like an arrow pointing to the right.
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And that is how we tell it that we want to
run a method.
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The method that we're gonna run is
getMessage.
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So get and then capital m message.
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And remember it is a method, or also a
function, so
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that means to call a function, we need to
use the open and close parentheses.
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So we'll go ahead and do that.
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And then close it, save, and now let's
refresh and see what the difference is.
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Okay, connection successful, so I'll go in
here, break it again.
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Save our file, then refresh.
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And so now it actually gives us an
informative message more than just sorry,
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I can't connect.
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It actually tells you SQL state hey, we're
unable to open the database file.
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All right, so that tells us we can't open
the file, maybe we did a mistake in
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our connection string, which now we know
we did, so I'll go and
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close that out and then hit Save.
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Okay, the final step, the last thing that
we want to do, is a command on the actual
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PDO object itself or a method on the PDO
object itself.
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So we need to go ahead and
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open up a new tab to search for the actual
PHP PDO object.
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So we'll do PDO class.
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Then the PHP PDO class is in the manual.
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Okay and if you scroll down here you'll
see that
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there are several different methods.
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The one that we're interested in is
setAttribute.
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So we say, setAttribute.
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And then in here, you'll see there are
several constants or
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the actual attributes that you can change.
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That's here in the header.
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So you'll see attribute case, and then
attribute error mode.
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So attribute error mode or the error
reporting is what we want to modify.
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So we wanna, scroll down a little bit more
here.
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We wanna modify this so that the error
mode, when that happens,
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anything that happens at all instead of
silencing them or having a little warning.
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We actually wanna set it to throw
exception.
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So no matter what the error is, we're
gonna throw an exception.
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So let's go ahead and do that by calling
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setAttribute on our actual PDO object,
or the dollar sign DB.
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So I'll head back over to our index.php
file and we'll do it directly underneath.
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So we're gonna get rid of this, and we
don't need this guy anymore.
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And then here, we're gonna do $db, object
operator to setAttribute.
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All right, and then close that line with a
semicolon.
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Now if you go back to where we were in the
manual.
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You'll see that we have the attribute and
then the value.
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So, our attribute that we're gonna set,
copy this constant here,
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and we're gonna paste that in.
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That's our first argument.
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Then we're gonna add a comma and
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our second argument is the mode that we
want to set it to.
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And that would be PDO error mode
exception.
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Copy that paste it in.
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Hit Save, and then I'm gonna do my preview
just to make sure it's all good.
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Okay, we didn't do the var dump, so we
wouldn't see anything different, but
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there's no errors, no exceptions, nothing
dying out.
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It seems like we're right where we wanna
be.
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Let's go ahead and close this guy out.
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And then go back and review here.
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So we've added a try catch statement to
make sure there are any exceptions that
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happen on the PDO connection string, will
throw an error message to us and
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then die out the script.
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And then we also after creating the new
PDO object,
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we have set the error mode attribute of
the PDO object or
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the DB object, to throw all exceptions for
any kind of error that happens.
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Next up we wanna run some queries and see
what films are in our database.
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