About this lesson
Learn how to use if/else/elseif statements to test against conditions.
Exercise files
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Conditional Statements.docx199.5 KB Conditional Statements - Solution.docx
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Quick reference
Conditional Statements
Conditional statements allow us to test against conditions.
When to use
Any time you want to test against a condition and take some action based on that condition, use a conditional statement.
Instructions
The main conditional statements are IF, IF/ELSE, and IF/ELSEIF.
An If Statement takes this form:
if (condition) {
// do something
}
And if/else statement takes this form:
if (condition) {
// do something
} else {
//do something else
}
An if/elseif statement takes this form:
if (condition) {
// do something
} elseif (condition 2) {
//do something
} else {
//do something else
}
Hints & tips
- The main conditional statements are If, If/Else, and If/Elseif
- Use our comparison operators and logic operators as the conditions
- 00:04 Okay, in this video, we're gonna talk about conditional statements.
- 00:07 Conditional statements are, basically, if L statements or if L ifs statements.
- 00:13 And they allow us to compare two things and
- 00:15 take some sort of action based on that comparison.
- 00:18 So we've looked at comparison operators in the past.
- 00:20 We've looked at logic operators, now we finally get to actually use this stuff, so
- 00:24 let'=s erase all of this and let's create a couple of variables, $num1 =
- 00:29 10 and let's go, $num2 = 2.
- 00:34 This is the basic structure of an if statement,
- 00:37 it's if (condition) do something and that pretty much easy.
- 00:42 Here's where we put our conditions and
- 00:44 this is where we use our comparison operators.
- 00:46 So let's say, if ($num1 >
- 00:51 $num2) then { echo "$num1
- 00:56 is greater than $num2"; }.
- 01:01 There we go.
- 01:03 So let's save this, come over here, hit reload.
- 01:06 10 is greater than two.
- 01:07 That's correct.
- 01:08 Now, what if we change $num2 into 20?
- 01:12 We get nothing or why, all because here, we're saying if $num 1 > $num2,
- 01:17 do this, otherwise, don't do anything.
- 01:20 It tests this out, it finds this to be false and so it stops,
- 01:24 it doesn't do this line.
- 01:26 Now if we wanted to do something else, we can type in else and
- 01:31 then just like this do something else.
- 01:33 So we can, echo "$num1 is NOT greater than $num2";,
- 01:40 save this and hit reload, 10 is not greater than 20.
- 01:46 If we change this back, save it and hit reload, 10 is greater than 2.
- 01:51 This is your basic conditional statement and
- 01:54 in here we can do any sort of thing we want, greater than, equal to identical.
- 02:00 Remember that comparison operator, all our comparison operators work here and
- 02:05 also our logic operators.
- 02:06 Remember and $num1 = 10.
- 02:13 So now it we'll compare two of these things, now both of these have to be true,
- 02:17 in order for this to spit out that, otherwise, we do that.
- 02:21 You do or, we can do xor,
- 02:23 all of the things we talked about in our logic operators video.
- 02:27 That's how you do those things.
- 02:28 So that's very cool.
- 02:29 So that's if and else.
- 02:30 There's one more thing.
- 02:31 You can do an else if statement, and
- 02:34 that allows you to test more than one thing, right?
- 02:38 So if $num1 > $num2; } elseif.
- 02:45 And now we can run another conditional, $num1 == 50.
- 02:50 Then echo, let's say,
- 02:55 ($num1 is 50).
- 02:58 So if we save this, hit reload, we see 10.
- 03:01 Whoops.
- 03:04 Forgot to put, I told you we'd always forget semicolons here and
- 03:07 there, even to this day I still do.
- 03:08 Okay, so, 10 is greater than 2.
- 03:10 So let's change this around, let's change $num1 to 50.
- 03:13 If $num1 is greater than $num2, well let's just hit reload and see what happens.
- 03:19 50 is greater than 2.
- 03:21 Why didn't this get executed?
- 03:23 Well, because this was already true.
- 03:26 If this is true, this gets executed and the whole thing stops.
- 03:30 If it's not true, then it drops down and it tries this.
- 03:34 So if we change this to less than and saved.
- 03:39 50 is 50 because this is not true.
- 03:43 This condition, right here, is not true.
- 03:45 So we drop down and we try the elseif statement and
- 03:49 this is true because 50 is equal to 50.
- 03:52 So it prints this out and it stops, it doesn't do this.
- 03:55 If this isn't true, and this isn't true, then we would else that out.
- 04:00 So let's give this a try.
- 04:02 Let's go 40.
- 04:03 Save this.
- 04:04 40 is not greater than 2,
- 04:06 cuz this wasn't true, this wasn't true, so we outputted that.
- 04:11 That's a conditional statement.
- 04:12 Very, very useful.
- 04:13 You will use this a thousand times in your lifetime, more than that.
- 04:16 It's just very, very important to all programming languages.
- 04:19 And this is how you do it in PHP.
- 04:21 Conditional statement,
- 04:22 remember, you could do all your comparison operators inside these parentheses.
- 04:26 You can also do all your logic operators in there.
- 04:28 It's a great way to control the flow of your code.
- 04:31 That's all for this video and in next video,
- 04:32 we'll look at switch, which is another type of conditional statement.
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