Anatomy of a PHP Script

• every PHP script is made up of statements.


• each statement must be terminated with a semicolon.
  Example:
  
some_instruction();
$variable = 'value';
  

Note:

The last instruction before a closing tag does not require a semicolon, but it is advisable to always terminate an instruction with a semicolon.

Comments

Types of PHP comments:

1.  // Single line comment




2.  # Single line comment




3.  /* Multi-line
       comment
     */




4.  /**
     * API Documentation Example
     *
     * @param string $bar
     */
     function foo($bar) { }

Note:

Because the closing tag ?> will also end a comment, code like:

// Do not show this ?> or this 

will output:

or this

• because the single line comment was terminated by ?>


• Normally, a single line comment should be terminated with a newline (\r, \n or \r\n)

Whitespace

PHP is whitespace-insentive, except with this few limitations:

1. You cannot have any whitesapce between <? and php


2. You cannot break apart keywords
   ex. whi le, fo r, and funct ion


3. You cannot break apart variable names and function names
   ex. $var name and function foo bar()

Code Block

A series of statements enclosed between two braces:

{
    // some comments 
    f(); // a function call
}

• used in creating groups of script lines that must all be executed under specific circumstances, such as a function call or a conditional statement.


• code blocks can be nested.

Language Constructs

Elements that are built-into the language that follow specific rules.
Ex.

   echo 10; // will output 10
   print (10); // will also output 10
   exit(); // terminate the script and either output a string or return a numeric status 
   die();   // an alias of exit()

Note:

echo is not a function and therefore does not have a return value