- Escaping to PHP
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:
Canonical PHP tags
The most universally effective PHP tag style is:
If you use this style, you can be positive that your tags
will always be correctly interpreted.
Short-open (SGML-style) tags
Short or short-open tags look like this:
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
ASP-style
tags mimic the tags used by Active Server Pages to delineate code blocks.
ASPstyle tags look like this:
To use ASP-style tags, you will need to set the
configuration option in your php.ini file.
HTML script tags
HTML script tags look like this:
- Commenting PHP Code
- 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.
Multi-lines printing: Here are
the examples to print multiple lines in a single print statement: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.
3. PHP is whitespace insensitive
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:
- PHP is case sensitive
Yeah it is true that PHP is a
case sensitive language. Try out the following example:
This will produce the following
result
- Statements are expressions
terminated by semicolons
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 $greeting:
- Expressions are
combinations of tokens
The smallest building blocks of PHP are the indivisible
tokens, such as numbers (3.14159), strings (.two.), variables ($two), constants
(TRUE), and the special words that make up the syntax of PHP itself like if,
else, while, for and so forth
- Braces make blocks
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.
- Running PHP Script from Command Prompt
Yes you can run your PHP script
on your command prompt. Assuming you have the following content in test.php
file
Now
run this script as command prompt as follows:
It
will produce the following result
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