Hi, this intro won't be too long. Finally, in the third part we'll start learning PHP
Today we will be creating a simple script for checking user's age, based on their input
When we have this explained and our environment is set, off we go.
Table of contents
This article won't be too long - today we will learn how to
- Display text and HTML in PHP
- Use
$_GETsuperglobal and basics of form handling - Write basic conditional statements with
if-elseconstruct
So, maybe let's start with executing code
Executing code in PHP
Do you remember the code from pt.1 of this course? This one
<?php
echo "Hello World";
?>
And it displays Hello World- but first we see this - <?php
What does it mean? It's the opening of php tag.
PHP will only get executed if it's inside <?php ?> tags - every file with PHP code has them inside.
There can be multiple PHP tags inside one file
And if we only have PHP code inside file (So no additional HTML) you can omit closing tag (?>)
What does it mean? It means that code from above can also be rewritten as
<?php
echo "Hello World";
(Of course, only if this is only thing in the file)
By the way, in older codes you can see tags written like this <? ?>. These are short tags. For portability reasons, you shouldn't use them. Some servers have this function disabled by default - so your code won't work
So, let's create a new folder inside htdocs called age-checker,
add index.php file inside it and open it in your code editor
At first - I created a simple form
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Age checker</title>
</head>
<body>
<h1>Are you old enough to access this page?</h1>
<form action="" method="GET">
<input type="number" name="age" id="" placeholder="Enter your age">
<button type="submit">Check age</button>
</form>
</body>
</html>
If you don't understand content - check my recent article from this series
Now, after we run it - we should see this
(Note: Remember, that to execute PHP you need to have your environment running and head to http://localhost/[path_to_your_file] to execute it)
Okay, form is present - but what about it's logic?
Let's write it. Add php tags (<?php ?>) after form
<?php
?>
Now inside it, we need to check if we got something from the form
if(!isset($_GET['age'])){
exit();
}
These lines mean "If $_GET['age'] is not set (!), finish the script"
What is this - $_GET['age']?
That's how we get data from GET form - inside single quotes we place name of the field. But about it, later in this course
And let's look at the if too - basic structure looks like this
if(condition){
code
}
Similar to other programming languages - this code means
If the condition is true, execute code
When we are sure, that code won't be executed. Let's start writing our conditions
First - If user isn't and adult (is less than 18 years old) display proper message
if($_GET['age'] < 18){
echo "<p>Access denied - You are too young to visit this website</p>";
}
We should look at the condition?
$_GET['age'] < 18
Do you remember comparing 2 numbers in math? That's what we do here
That piece of code can be read as
Is
$_GET['age']smaller than 18? If yes, display<p>Access denied - You are too young to visit this website</p>
But, what if we actually meet that condition? Let's code it too
Delete closing brace, and add
}else{
echo "<p>Access granted - Welcome";
}
Now, we added a alternative. If that condition isn't met - execute this code. Let's add one more thing.
As developers we have to make our code as foolproof as possible. Someone may try to send us text instead of the number
To check if something is a number we use is_numeric function
Don't worry, if you can't understand something - I'll talk more about types of data in the next. But let's go back of the code
In between those 2 ifs, add one more
if(!is_numeric($_GET['age'])){
echo "<p>Your age must be a number</p>";
exit();
}
What is this exclamation mark (!)? It's negation.
is_numeric gives us true or false
And !is_numeric($_GET['age']) means
Is
$_GET['age']not numeric?
This ! means not
And, that's it. The end of this article
Afterword
Congratulations, you have successfully wrote and (hopefully) understood PHP code.
We finally got to the point, where we write PHP. But don't worry, now we will be writing PHP 99% of the time
Yes, I know. It was a bit delayed. But here you have it
Thanks for reading, leave your feedback in the comments and that's it
See you in next articles. Pt.4 will be published next thursday
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