PHP Syntax Overview
This chapter will give you
an idea of very basic syntax of PHP and very important to make your PHP
foundation strong.
The PHP parsing engine
needs a way to differentiate PHP code from other elements in the page. The mechanism
for doing so is known as 'escaping to PHP.' There are four ways to do this:
The most universally
effective PHP tag style is:
|
<?php...?>
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If you use this style, you
can be positive that your tags will always be correctly interpreted.
Short or short-open tags
look like this:
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<?...?>
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Short tags are, as one
might expect, the shortest option You must do one of two things to enable PHP
to recognize the tags:
- Choose the --enable-short-tags configuration
option when you're building PHP.
- Set the short_open_tag setting in
your php.ini file to on. This option must be disabled to parse XML with
PHP because the same syntax is used for XML tags.
ASP-style tags mimic the
tags used by Active Server Pages to delineate code blocks. ASP-style tags look
like this:
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<%...%>
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To use ASP-style tags, you
will need to set the configuration option in your php.ini file.
HTML script tags look like
this:
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<script language="PHP">...</script>
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A comment is
the portion of a program that exists only for the human reader and stripped out
before displaying the programs result. There are two commenting formats in PHP:
Single-line
comments: They are generally used for short explanations or notes
relevant to the local code. Here are the examples of single line comments.
|
<?
# This is a comment, and
# This is the second line of the comment
// This is a comment too. Each style comments
only
print "An example with single line
comments";
?>
|
Multi-lines
printing: Here are the examples to print multiple lines in a single
print statement:
|
<?
# First Example
print <<<END
This uses the "here document" syntax
to output
multiple lines with $variable interpolation.
Note
that the here document terminator must appear
on a
line with just a semicolon no extra
whitespace!
END;
# Second Example
print "This spans
multiple lines. The newlines will be
output as well";
?>
|
Multi-lines
comments: They are generally used to provide pseudocode algorithms and more
detailed explanations when necessary. The multiline style of commenting is the
same as in C. Here are the example of multi lines comments.
|
<?
/* This is a comment with multiline
Author : Mohammad Mohtashim
Purpose: Multiline Comments Demo
Subject: PHP
*/
print "An example with multi line
comments";
?>
|
Whitespace is the stuff you
type that is typically invisible on the screen, including spaces, tabs, and
carriage returns (end-of-line characters).
PHP whitespace insensitive
means that it almost never matters how many whitespace characters you have in a
row.one whitespace character is the same as many such characters
For example, each of the
following PHP statements that assigns the sum of 2 + 2 to the variable $four is
equivalent:
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$four = 2 + 2; // single spaces
$four
<tab>=<tab2<tab>+<tab>2 ; // spaces and tabs
$four =
2+
2; // multiple lines
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Yeah it is true that PHP is
a case sensitive language. Try out following example:
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<html>
<body>
<?
$capital = 67;
print("Variable capital is
$capital<br>");
print("Variable CaPiTaL is
$CaPiTaL<br>");
?>
</body>
</html>
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This will produce following
result:
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Variable capital is 67
Variable CaPiTaL is
|
A statement in
PHP is any expression that is followed by a semicolon (;).Any sequence of valid
PHP statements that is enclosed by the PHP tags is a valid PHP program. Here is
a typical statement in PHP, which in this case assigns a string of characters
to a variable called $greeting:
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$greeting = "Welcome to PHP!";
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The smallest building
blocks of PHP are the indivisible tokens, such as numbers (3.14159), strings
(.two.), variables ($two), constants (TRUE), and the special words that make up
the syntax of PHP itself like if, else, while, for and so forth
Although statements cannot
be combined like expressions, you can always put a sequence of statements
anywhere a statement can go by enclosing them in a set of curly braces.
Here both statements are
equivalent:
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if (3 == 2 + 1)
print("Good - I haven't totally lost my mind.<br>");
if (3 == 2 + 1)
{
print("Good - I haven't totally");
print("lost my mind.<br>");
}
|
Yes you can run your PHP
script on your command prompt. Assuming you have following content in test.php
file
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<?php
echo
"Hello PHP!!!!!";
?>
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Now run this script as
command prompt as follows:
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$ php test.php
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It will produce following
result:
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Hello PHP!!!!!
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Hope now you have basic
knowledge of PHP Syntax.
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