To Run or Not to Run - Making Decisions

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We need to make decisions about the state as well as information in order to determine whether to run a block of code or not. There are multiple constructs available for us to use. In this episode, we’ll focus on the if/else if/else construct. We’ll look at different code examples in the Genesis framework and twentyseventeen themes. We’ll also talk about conditional expressions.

The code that is controlled by the decision is enclosed within the curly braces (there is alternative syntax that uses a colon for the opening curly brace and endif; for the closing one). For that code block to run, the conditional expression must be true.

When you have different branches to the decision with elseif and/or else the code within those respective code blocks runs only if the main if conditional expression is false and its conditional expression is true.

With this structure, only one or none of the code blocks run. They only run if the preceding branch is false and its conditional expression is true.

Conditional Expressions

We will talk more about the conditional expression as well as the different operators you can use, such as an “or”, “and”, equality, greater than, not equal to, and more. There are logical operators such as || (which is an “or” operation) and && (which is an “and” operation). You also have comparison operators such as greater than, less than, equal to, etc.

We talk briefly about type juggling as we cover the difference between == and ===. You can learn more about type juggling in Docx as well as in the PHP Variables Bootcamp lab.

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Challenge Yourself

When will the code within an 'else' run?: When the preceding if and elseif are not true, then it will run. Remember that only one branch in the structure will run if one of them is true.

	<?php

	$post_id = 10;
	$image_size = 'thumbnail';

	if ( $image_size == 'full' \|\| $post_id < 5 ) {
	// run the if code block
	} elseif ( $image_size == 'thumbnail' && $post_id == 10 ) {
	// run the elseif code block
	} else {
	// do the else code block.
	}

view raw code-challenge.php hosted with ❤ by GitHub

For the above code, which code block is going to run?

The elseif code block will run. Why? The image size is set to “thumbnail.” Therefore the first part of the conditional expression is true. The post id is set to 10. Therefore, the second conditional expression is also true. With an “and” comparison operator, both sides have to be true.

But also notice that the if is false. It checks that conditional expression first. When it is found to be false, then it goes to the elseif.

For the following conditional expression, will it evaluate to True or False: 10 === '10'?

False. Why?

It’s using the strict comparison operator which says both the data type and the value has to be the same.

Additional Resources

Know the Code has plenty of content available for you to learn deeply about decisions and conditional expressions. Links are provided above. But here are some keys that I want to point out for you:

Episode #4
10:39 Runtime

Decision Branching - if/then/elsefree

Lab: Building Blocks of Programming

Let's talk about decision branching and more specifically about the "if/then/else" constructs. Decisions control the flow of your program. The branch only runs when the conditional control statements is true.

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7 Episodes
01:07:16 Runtime

PHP Conditional Expressions

Conditional expressions are an essential in programming, yet they are largely misunderstood. In this bootcamp lab, you will discover how complex expressions are evaluated as well as falsey states, assignments in the expression, and much more. Roll up your sleeves as it's time to dive deep into PHP conditional expressions.

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