PHP: 'Hello, World!' Program

As in any programming language, we start by writing our first 'Hello, World!' program in PHP. PHP scripts are mostly run and displayed in a browser, but they can also be run from the command-line.

PHP 'Hello, World!' from the Command Line

Open a text editor (say Gedit, Leafpad, Lime Text or whatever available), create a new file, and type in the below PHP code (or copy & paste it from here) 

					
						<?php 
							echo 'Hello, World!';  
						?>

Save the file as hello.php. Below we note some of its basic syntax:

  • PHP code begins with the open tag <?php and ends at ?>.
  • echo is a PHP language construct for sending texts/strings, variable values and HTML snippets into the browser.
  • Statements in PHP end with a semicolon (;). The echo statement in the above program ends with a semicolon.
  • PHP files have the extension .php

We can execute the above PHP file from the command line, typing 

					
						$ php hello.php

We can also execute PHP as a shell script. Add the #!/usr/bin/php shebang interpreter directive to the file as its first line of script. The path could be different for different operating systems; type 

					
						which php

to confirm. In Mac and Linux systems, it is usually 

					
						/usr/bin/php

So, the shell script is 

					
						#!/usr/bin/php
						<?php 
							echo 'Hello, World!';  
						?>

Next, we type a command in the terminal to mark hello.php as executable 

					
						chmod u+x hello.php

The script file can now be executed from the terminal by running the command 

					
						./hello.php

PHP 'Hello, World!' in a Browser

In this section, we will embed our PHP 'Hello, World!' script from the above section in HTML, run and see the output in a web browser. The steps are outlined below.

1) Create a PHP project directory

If you are using a Mac, you can go to the working directory created as shown in the Step 3 of our previous tutorial. If you name your working directory as /Sites, navigate to it 

						
						$ cd /users/username/Sites

If you are using a Linux system, navigate to /var/www/html 

						
						cd /var/www/html

Now create a project directory there, say, hello 

						
						sudo mkdir hello

Navigate again to the newly created hello directory 

						
						cd hello

2) Create hello.php

Open a text editor, create a new file, and type in the below code (or copy & paste it from here) containing our embedded 'Hello, World!' PHP script in the HTML 

						
							<!DOCTYPE html>
							<html>
							<head>
							<title>Hello, World! Page</title>
							</head>
							<body>
							<?php 
								echo 'Hello, World!';  
							?>
							</body>
							</html>

Save the file as hello.php.

3) Start Apache

If you are using a Mac, start the Apache server by typing the below command into the terminal 

						
						apachectl start

If you are using a Linux system, type 

						
						sudo /etc/init.d/apache2 start

After starting the server, type http://localhost/hello/hello.php in the URL bar of your web browser. The resulting screen should look something like the one shown below

PHP 'Hello, World!' Page

4) View Source Code

Now right-click on the page and select View page source from the context menu (or just do Ctrl+U)

PHP 'Hello, World!' Page Source

In the page source, we find neither the open tag <?php nor the end tag ?> we typed. We do not find the echo statement either. What happened here?

When the browser sends an HTTP request to the web server for a .php file, the server first sends the .php file to the PHP interpreter. The PHP interpreter checks for PHP sections inside the file. When it finds an open tag <?php, it runs the code inside it till the end tag ?>, and replaces the code with its output. The server then sends the result back to the browser, which is what we saw on doing Ctrl+U.

Notes

  • A heap of detailed information about your current installed PHP like version, file locations, configuration, predefined variables, environment, HTTP headers, etc can be obtained from the phpinfo() function. Just invoke it. 
    							
								<?php 
									phpinfo();  
								?>