PHP
5 Syntax
A PHP script
is executed on the server, and the plain HTML result is sent back to the
browser.
Basic PHP
Syntax
A PHP script
can be placed anywhere in the document.
A PHP script
starts with <?php and ends with ?>:
<?php
// PHP code
goes here
?>
The default
file extension for PHP files is ".php".
A PHP file
normally contains HTML tags, and some PHP scripting code.
Below, we
have an example of a simple PHP file, with a PHP script that uses a built-in
PHP function "echo" to output the text "Hello World!" on a
web page:
Example
<!DOCTYPE
html>
<html>
<body>
<h1>My
first PHP page</h1>
<?php
echo
"Hello World!";
?>
</body>
</html>
Note: PHP statements end with a semicolon
(;).
Comments in
PHP
A comment in
PHP code is a line that is not read/executed as part of the program. Its only
purpose is to be read by someone who is looking at the code.
Comments can
be used to:
Let others
understand what you are doing
Remind
yourself of what you did - Most programmers have experienced coming back to
their own work a year or two later and having to re-figure out what they did.
Comments can remind you of what you were thinking when you wrote the code
PHP supports
several ways of commenting:
Example
<!DOCTYPE
html>
<html>
<body>
<?php
//
This is a single-line comment
#
This is also a single-line comment
/*
This
is a multiple-lines comment block
that
spans over multiple
lines
*/
//
You can also use comments to leave out parts of a code line
$x
= 5 /* + 15 */ + 5;
echo
$x;
?>
</body>
</html>
PHP Case
Sensitivity
In PHP, all
keywords (e.g. if, else, while, echo, etc.), classes, functions, and
user-defined functions are NOT case-sensitive.
In the
example below, all three echo statements below are legal (and equal):
Example
<!DOCTYPE
html>
<html>
<body>
<?php
ECHO
"Hello World!<br>";
echo
"Hello World!<br>";
EcHo
"Hello World!<br>";
?>
</body>
</html>
However; all
variable names are case-sensitive.
In the
example below, only the first statement will display the value of the $color
variable (this is because $color, $COLOR, and $coLOR are treated as three
different variables):
Example
<!DOCTYPE
html>
<html>
<body>
<?php
$color
= "red";
echo
"My car is " . $color . "<br>";
echo
"My house is " . $COLOR . "<br>";
echo
"My boat is " . $coLOR . "<br>";
?>
</body>
</html>
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