How to Write Your Very First PHP Program
Advanced programmers know a secret. The secret
that they know relates to how a PHP program is constructed.
Here is the secret:
"Complex programs are built up from simple
programs. If you can learn how to create a simple program, you can
learn how to build a complex program, no matter how complicated."
A program can be constructed of only a few lines.
They always start the same way. Start with the PHP start tag, followed
by your programming code, and last by the PHP end tag.
Example 1:
Line 1: <php
Line 2: // your program goes here
Line 3:?>
The PHP program shown above has only 3 lines. Line
1 & 3 are the start and end tags, line 2 is your functional
code. In this case however, line 2 is a comment and will not perform
any specific action other than to remind you of something. Comments
are not processed by the interpreter. Once a comment is encountered,
it is basically ignored.
Example 2:
Line 1: <php
Line 2: // this is one comment
Line 3: // this is another comment
Line 4: // this is the last comment
Line 5:?>
The code in example 1 behaves exactly as the code
in example 2. Even though example 2 has 2 more lines. If you noticed,
the additional lines in example 2 are only comments. Once again
they are ignored by the PHP interpreter (PHP Engine).
If there is one comment or multiple comments, the
interpreter will act the same way. It will ignore any comments that
it finds.
Example 3:
Line 1: <php
Line 2: // below this line is a real PHP programming command
Line 3: echo 'My First Real Program';
Line 4:?>
In example 3 you will see your first functioning
PHP program. The 'echo' command was added to this program, located
on line 3. An 'echo' statement is a built in PHP command that will
output whatever follows it to the screen. Anytime you want to output
something using PHP to the screen, web browser, or visual display.
Use the simple 'echo' command.
As you can see, the words 'My First Real Program'
follows the 'echo' command. It is very important to enclose the
words that you want 'echoed' on the screen inside single or double
quotes. This way the echo command knows from what character to start
with, and what character to end with, as it generates the output
to the screen.
When the echo command is called, it takes the contents
inside the quotes, and sends it out to the screen - minus the quotes.
So the output would be:
My First Real Program
Example 4:
Line 1: <php
Line 2: // the next line is the first echo command
Line 3: echo 'You are ';
Line 4: // the next line is the second echo command
Line 5: echo 'learning how to ';
Line 6: // the next line is the last echo command
Line 7: echo 'program in PHP.';
Line 8:?>
The output to this program would be:
You are learning how to program in PHP.
When you start programming, there is no limit to
how many comments and commands you can enter in your program. Go
ahead, try it yourself. As you get better you won't need so many
comments to remind you of what you are doing in your program.
Complex programs are made up of simple programs.
Learning how to mix simple commands together, along with PHP start
and end tags makes a fully functioning PHP program. As you are learning,
a good suggestion is to add as many comments as you need to help
remember what you are doing. Comments are like taking notes that
you can refer back to. As you get better at programming, you will
naturally enter less comments. The PHP 'echo' command outputs characters
to the screen. Enclose all characters after an 'echo' command with
single or double quotes.
Congratulations, you just wrote your first PHP
program.
* * *
Paul Markovich is a Lead Technical Trainer.
He has been designing and building custom web sites
for entrepreneurs since 1997. He'll help you get the answers to
your burning open source programming questions!
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