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Managing 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.
If you are unable to trigger an Exception by just misspelling the database name, try changing it to look in a different location.
Such as:
$db = new PDO('sqlite:/database.db');
Notice the / instead of the ./ which is a very common error.
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Managing errors in any application is very
important,
0:00
especially when it comes to database
errors.
0:03
We will manage this by wrapping our code
that communicates with
0:06
the database within a try catch block.
0:08
Continuing where we left off, we have
created our PDO object successfully.
0:12
And then I demonstrated how we can break
that, so, we're gonna go ahead and
0:17
break that again.
0:21
So, I'm gonna add a few more A's back in
and
0:22
see how we can handle these errors and
exceptions.
0:25
Let's go ahead and refresh this.
0:28
And now we'll see we have a fatal error,
uncaught exception.
0:30
Well, we don't want that to happen.
0:34
And if you recall from object-oriented
code practice.
0:35
We have a lot of try-catch statements when
we're trying to catch exceptions and
0:39
handle errors.
0:42
So that's what we're gonna do, we're gonna
handle this PDL exception,
0:44
by catching any general exceptions in our
script.
0:47
So head back over to the index.php file.
0:51
And then here we're gonna surround any
connection to the database.
0:54
So here where we're creating our new
database,
0:58
we're gonna actually surround that in a
try-block.
1:01
So try, then open and close our curly
braces.
1:05
Then we have a catch.
1:10
Open and close parens.
1:13
And then open and close our curly braces.
1:16
Now, this is try catch block.
1:18
Inside of here, we're gonna try any code
that we wanna run.
1:20
And if it fails out or has an exception,
we want to catch that exception.
1:25
So here we just simply put the class that
we want to catch,
1:30
which is a PDO Exception, or we can use
the parent class to catch any exception.
1:33
So, we'll type in Exception with a capital
E.
1:39
And then the next argument is the actual
exception object that gets
1:44
thrown when the error happens.
1:49
So that one we'll just call it dollar sign
e for exception.
1:51
Now we want to take this code here on line
11.
1:55
In fact we'll do line 11, 12.
1:57
We'll just copy it all.
2:00
And we'll put it inside of our try block.
2:03
So that way anything inside of
2:07
here will happen only if the succesful
database object is created.
2:09
So the other half of this coin here or the
other side of
2:15
this coin is to actually put something in
here for our exception when that happens.
2:18
So right now I'm just gonna echo a string.
2:24
In that string let's say, sorry, the
connection was not successful.
2:27
Okay?
2:37
And then I also don't want it to continue
so I'll add another die statement here.
2:38
[BLANK_AUDIO]
2:42
Close it with a semicolon.
2:44
Save our file.
2:46
And I'm gonna refresh.
2:47
So instead of it throwing an uncalled
exception, now it says,
2:49
sorry the connection was not successful.
2:52
Much cleaner, much nicer, no weird dumps
to the screen about our code.
2:53
Exactly what we want.
2:58
Now to make sure it works, we're gonna go
ahead and fix our error and then
2:59
back in here, save our file, and then
let's redo our preview.
3:07
And now we have our PDO object.
3:13
Before we continue on we do want to do 2
more things to our try-catch block or
3:16
to our PDO object and
3:21
then our actual exception to make it a
little bit more informative for us.
3:23
So let's go ahead over to a new tab and
let's open up the exception class.
3:28
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.
3:38
If we scroll down here,
3:44
we'll see that we have several different
methods that we can use.
3:45
The one that we're going to want is
getMessage, which if we click on
3:48
getMessage information it'll just say it
gets the exception message, and
3:53
returns the exception message as a string.
3:58
Head back over to your code, here I'm
going to modify line 11,
4:01
I'm going to actually get rid of
everything there just to echo.
4:05
I'm gonna pass through the actual
exception object.
4:09
Just dollar sign e.
4:11
And then an object operator.
4:14
So that's a dash and a greater than
symbol.
4:16
Looks like an arrow pointing to the right.
4:18
And that is how we tell it that we want to
run a method.
4:20
The method that we're gonna run is
getMessage.
4:23
So get and then capital m message.
4:26
And remember it is a method, or also a
function, so
4:31
that means to call a function, we need to
use the open and close parentheses.
4:34
So we'll go ahead and do that.
4:39
And then close it, save, and now let's
refresh and see what the difference is.
4:41
Okay, connection successful, so I'll go in
here, break it again.
4:47
Save our file, then refresh.
4:53
And so now it actually gives us an
informative message more than just sorry,
4:56
I can't connect.
5:00
It actually tells you SQL state hey, we're
unable to open the database file.
5:01
All right, so that tells us we can't open
the file, maybe we did a mistake in
5:06
our connection string, which now we know
we did, so I'll go and
5:10
close that out and then hit Save.
5:13
Okay, the final step, the last thing that
we want to do, is a command on the actual
5:16
PDO object itself or a method on the PDO
object itself.
5:22
So we need to go ahead and
5:26
open up a new tab to search for the actual
PHP PDO object.
5:28
So we'll do PDO class.
5:33
Then the PHP PDO class is in the manual.
5:36
Okay and if you scroll down here you'll
see that
5:40
there are several different methods.
5:42
The one that we're interested in is
setAttribute.
5:45
So we say, setAttribute.
5:49
And then in here, you'll see there are
several constants or
5:51
the actual attributes that you can change.
5:54
That's here in the header.
5:57
So you'll see attribute case, and then
attribute error mode.
5:58
So attribute error mode or the error
reporting is what we want to modify.
6:02
So we wanna, scroll down a little bit more
here.
6:08
We wanna modify this so that the error
mode, when that happens,
6:10
anything that happens at all instead of
silencing them or having a little warning.
6:14
We actually wanna set it to throw
exception.
6:19
So no matter what the error is, we're
gonna throw an exception.
6:22
So let's go ahead and do that by calling
6:26
setAttribute on our actual PDO object,
or the dollar sign DB.
6:30
So I'll head back over to our index.php
file and we'll do it directly underneath.
6:34
So we're gonna get rid of this, and we
don't need this guy anymore.
6:41
And then here, we're gonna do $db, object
operator to setAttribute.
6:47
All right, and then close that line with a
semicolon.
6:56
Now if you go back to where we were in the
manual.
6:59
You'll see that we have the attribute and
then the value.
7:02
So, our attribute that we're gonna set,
copy this constant here,
7:05
and we're gonna paste that in.
7:10
That's our first argument.
7:14
Then we're gonna add a comma and
7:15
our second argument is the mode that we
want to set it to.
7:17
And that would be PDO error mode
exception.
7:21
Copy that paste it in.
7:26
Hit Save, and then I'm gonna do my preview
just to make sure it's all good.
7:28
Okay, we didn't do the var dump, so we
wouldn't see anything different, but
7:34
there's no errors, no exceptions, nothing
dying out.
7:38
It seems like we're right where we wanna
be.
7:41
Let's go ahead and close this guy out.
7:43
And then go back and review here.
7:46
So we've added a try catch statement to
make sure there are any exceptions that
7:48
happen on the PDO connection string, will
throw an error message to us and
7:52
then die out the script.
7:58
And then we also after creating the new
PDO object,
7:59
we have set the error mode attribute of
the PDO object or
8:03
the DB object, to throw all exceptions for
any kind of error that happens.
8:07
Next up we wanna run some queries and see
what films are in our database.
8:13
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