Getting Started with PHP

PHP (Hypertext Pre-processor) is a web server-side programming language. It enables developers to build web applications that interact with databases. <!--more-->

Why PHP? #

PHP can be used to do many things. Let's look at some of the reasons why PHP is used:

• PHP is platform-independent. Therefore it can run on major operating systems. ie. Mac OS, Windows, or Linux.
• It can run on all modern servers such as Apache.
• PHP can be integrated with databases like MariaDb.
• It is easy to learn and implement.
• PHP frameworks are used by web developers to build web apps faster.

Here are some of the most popular PHP frameworks:

• Yii 2 -- A generic PHP framework used when developing web applications with many ties.
• Laravel -- A PHP framework designed to make web apps easier and faster for developers.
• FuelPHP -- A PHP framework that supports data-oriented web applications.

Prerequisites #

Before starting this tutorial, make sure you have installed Xampp. You can download Xampp here.

In this tutorial, we will be using Ubuntu.

Once the installation is complete, a /opt/lampp folder will be created.

Start Xampp by running the following command:

$ sudo /opt/lampp/lampp start

Starting XAMPP for Linux 7.4.10-0...
XAMPP: Starting Apache...ok.
XAMPP: Starting MySQL...ok.
XAMPP: Starting ProFTPD...ok.

Creating the PHP files #

Navigate to /opt/lampp/htdocs and create a new folder hello. This is where we will have our PHP files. Open a terminal and run the command below.

$ cd /opt/lampp/htdocs
$ sudo mkdir hello
$ cd hello

Then, create a new file index.php in /opt/lampp/htdocs/hello using this command.

$ sudo touch index.php

Then, open the file using Gedit by running the following command.

$ sudo gedit index.php

A hello world program #

We are going to write a simple PHP program. Let's look at the basic syntax of a PHP program. PHP code is written between <?php> and ?> tags in a PHP files as shown below.

<?php
//php code is written here
?>

In the index.php you created above put the following code:

<?php
 echo "<h1>Hello world!</h1>";
?>

We use the echo statement to display output on the screen. In the code above, we use the echo statement to display a HTML heading.

To run this code, open your browser at http://localhost/hello here, we append the folder name .ie hello to the base URL (http://localhost/).

You should see something like this image on your browser:

Congratulations! You have written your first PHP program.

Variables in PHP #

Variables are containers used for holding data types. When writing variable names, always make sure they start with a letter or an underscore but not a number.

In PHP, variables are created by writing the dollar ($) sign followed by the variable name. Let us look at a simple example.

<?php
$txt = "how old are you?";
$x = 25;
$y = 67;
?>

In this code, txt is a variable holding a string how old are you?, variable x holds the number 25, and variable y holds the number 67.

Conditional statements in PHP #

Conditional statements are used to perform some actions if a certain condition is adhered to.

They include:

• if statement - used to execute some code if a given condition is True.
• if... else statement - the if block is used to execute some code if a certain condition is true. If the condition is false, then the else block executes another block of code. This statement executes some code based on the true or false state of the condition.
• if... elseif...else statement - It is like the if ...else statement, but with the ability to check for multiple conditions.

Let's put each statement above in place:

1. The if statement #

Below is a syntax for an if statement.

if(condition){
 //code to execute
}

Let's look at an example.

<?php
$age = 15;

if ($age < 18) {
 echo "a kid!";
}
?>

Running this code gives "a kid!" as the output.

2. The if...else statement #

The syntax of an if else block looks like this:

if(condition){
  //code to execute if condition is true
}
else {
  //code to execute if condition is false
}

A simple implementation of the snippet above would look like this:

<?php
$age = 18;
if($age < 18){
 echo "a kid!";
}
else {
 echo "so youth!";
}
?>

The output should be: "so youth!". This is because the variable age is not less than 18. If we assign a value like 17 to variable age the output becomes "a kid!"

3. if... elseif... else statement #

The syntax of this statement looks as shown below.

if (condition) {
  // code to execute if condition is true;
} elseif (condition_2) {
 // code to execute if condition_2 is true
} else {
 // code to execute if none of the above are true
}

Implementing the above in a program would look like like this:

<?php
$age = "18";

if($age < "18"){
 echo "a kid!";
}
elseif($age > "35"){
 echo "a parent?";
}
else{}
 echo"a youth!";
?>

Since the variable age is equal to 18 the output of the code above is: "a youth!".

Comments In PHP #

Code commenting in PHP may be done for many reasons. For example, it can be used for documentation. A commented line is not executed as a part of the program.

There are 2 types of comments.

1. Single line comments #

This is a comment spanning a single line. Look at the example below.

<?php
 // this is an example of a single-line comment.
 echo"The output is:";
 # this is another one.
?>

As shown above, you can use 2 backslashes (//) or a hashtag (#) for single line comments.

2. Multi-line or block comment #

This is a comment spanning many lines. Here, you can use the symbols /* to open and */ to close the comment as shown below.

<?php
 echo "hello!!"
 /*
  This is a comment,
  that should span many lines
  */
?>

Conclusion #

In this tutorial, we have looked at the following:

• The syntax of a basic PHP program.
• Declaring variables in PHP.
• Using conditional statements.
• Code commenting in PHP.

Have a good PHP coding ahead.

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Peer Review Contributions by: Geoffrey Mungai