# Ifs, Else Ifs, Switch Updated on Jan 12, 2022 by [Alan Morel](/content/alanmorel/index.html) ## Table of Contents 1. [Logic](/content/classes/php/logic-conditionals#logic/index.html) 2. [Conditionals](/content/classes/php/logic-conditionals#conditionals/index.html) 3. [Switch Statement](/content/classes/php/logic-conditionals#switch-statement/index.html) 4. [Logical Operators](/content/classes/php/logic-conditionals#logical-operators/index.html) ## Logic **Logic** in any programming language is the ability for your program to make decisions and choose a path to take depending on the state. For example, if you're writing a calculator, you're going to have to perform different operations depending on what button the user presses. In this lesson, we'll learn all the ways to express logic in our [PHP](/content/classes/php/index.html) code by first learning about the comparison operators that make it possible. ### Equality Operator Using the **equality operator**, we can check if two numbers or "things" are equal to one another or not. If the things we are comparing are equal, using the equality operator on them will result in `true`, and if they are not equal, it will result in `false`. Using this operator is straightforward, simply use **three equal signs**. ```php ``` ```html 11 ``` ```php ``` ```html bool(true) bool(true) bool(false) ``` ### Inequality Operator The **inequality operator** works in a similar fashion but in the reverse. If what you're comparing is the same, the result will be `false`, otherwise it will return `true`. To use this operator, use a **single exclamation point followed by two equal signs**. ```php ``` ```html bool(false) bool(true) ``` ### Greater Than and Less Than Operators You can check if a numerical value is greater than or less than another one using the **greater than** and **less than** operators. ```php 19); $variable = 62; var_dump($variable > 25); var_dump($variable > 131); ?> ``` ```html bool(false) bool(true) bool(true) bool(false) ``` ### Or Equal To Operators In the case you need to check if a number is **either** equal to or greater/less than another number, there are operators specifically for that as well. To check if a number is **greater than or equal to** another number, use a greater than symbol followed by equal sign. On the flip side, to check if a number is **less than or equal to** another number, use a less than symbol followed by an equal sign. ```php = 76); var_dump(83 >= 92); ?> ``` ```html bool(true) bool(false) bool(true) bool(false) ``` ## Conditionals Now that we are able to compare things together and get back a boolean as a result, we are ready to make our program make decisions based off of that result. When we made decisions based off of the results of something, that is called a **conditional**. ### If The **if** statement is very straightforward. If whatever condition you are checking returns **true**, then the next block of code will execute. Let's say **if you eat 4 or more donuts, you will become sleepy**. ```php = 4) { echo('I am sleepy!'); } ?> ``` ```html I am sleepy! ``` Clearly you could care less about being sleepy, because you ate **5 whole donuts**. But what if you had some self-control and only ate **3 donuts**? ```php = 4) { echo('I am sleepy!'); } ?> ``` ```html ``` Nothing was printed because the code block did not run. The reason it did not run was because the conditional returned `false`, as 3 is not greater than or equal to 4. ### Else When you want to run a code block if the original conditional returns `false`, you can utilize the **else** keyword. Let's add an else block to our original situation. ```php = 4) { echo('I am sleepy!'); } else { echo('I can eat another donut!'); } ?> ``` ```html I can eat another donut! ``` Because this time we added the else code block, when the `$donuts <= 4` conditional returned false, it skipped the first code block and executed the second code block. ### Else If The **else if** keywords are a combination of both an if and an else block. You use these **in between** an if and an else statement and it serves as an additional path your code can take. ```php = 4) { echo('I am sleepy!'); } else if ($donuts === 3) { echo('I can eat another donut!'); } else if ($donuts === 2) { echo('I really want another donut!'); } else { echo('I NEED donuts'); } ?> ``` ```html I really want another donut! ``` First it compares 2 to 4, that's `false` so it moves on. Now it compares 2 to 3, that's also `false` so it continues on. Now it compares 2 with 2, and since that's `true`, the code executes. The final else is never called and the entire program moves on. ### Ternary Operator The **ternary operator** is the shorthand way to write an entire conditional on a single line. Use ternary operators to assign a variable a value depending on the outcome of the conditional. ```php = 4) ? 'Yes' : 'No'; echo('Am I sleepy? ' . $sleepy); ?> ``` ```html Am I sleepy? Yes ``` If you eat 4 or more donuts, the value of `$sleepy` will be `Yes`, otherwise it will be `No`. ## Switch Statement The **switch statement** offers us an alternative way to express a situation where you might have multiple else-ifs. A switch statement is similar to a traditionally else-if as you will see in the below example: ```php ``` ```html This weather is okay. ``` In our switch statement, we are **switching** on the `$weather` variable. If the value in it happens to match any of the cases we listed, the corresponding code block will execute. That is why it skipped over `rainy` and executed the code block under `cloudy`, as that was the value of `$weather`. The `break` statement is there to end the switch statement from continuing on to more cases. If none of the cases we defined match, we can add a `default` case so that something executes, no matter what. ## Logical Operators The conditions we have been evaluating so far have been pretty simple. However, there are cases where we'll want to evaluate multiple conditions at once before making a decision. There are many ways to combine and evaluate more than one condition at once, and we'll look at the **logical operators** that make that possible. ### And (&&) The **and** operator evaluates multiple conditions and only returns `true` if **both** conditions return `true`. ```php ``` ```html Since it is lunch time AND I am hungry, I should eat food now. ``` Since both conditions were `true`, the echo inside was executed. ### Or (| |) When you want the entire condition to be `true` if **either** condition is `true`, then what you want to use is the **or** logical operator. The or operator only requires a single condition to be `true` for the entire condition to be true: ```php ``` ```html There is something to eat! ``` Even though there was no burgers available, because there was pizza, the condition returned `true` and you were able to eat something. ### Not (!) The **not** operator negates the outcome of whatever condition it is placed in front of. If the original condition returned `false`, then adding a not operator in front would make it act as if it returned `true`, and vice-versa. ```php ``` ```html Since it is not raining, I can play basketball outside! ``` You cannot play basketball outside in the rain, so first you check if it's raining via the `$is_raining` variable. Since the weather is `sunny` and therefore not raining, you are able to play!