Variables are used for storing values.Variables in PHP start with a $ (dollar sign). They can be used to store numbers, strings or arrays. Once the variable is set, it can be used multiple times.PHP manages it automatically if you not specify variable data type.

Variables in PHP are case sensitive and by default are assigned by value.  Variable initialization is not mandatory.

PHP also has some predefined variables. Different categories of variables include:

$GLOBAL: References all variables available in global scope

$_GET — HTTP GET variables

$_POST — HTTP POST variables

$_SESSION — Session variables

$_REQUEST — HTTP Request variables

The above variables are also called super variables, as they have global scope; the scope will b define in below paragraph lines.

Example:

<?php

$sample =”Sample text”;

<?

Registration of Variables into Session:

By using the session_register() function, global variables in PHP can be registered. This function accepts different number of arguments, ( either variable that has  string or an array consisting of variable names or other arrays).

Example:
Session_register(“smple”);

$_session can also be used for registering variables.

Example:
$_SESSION['count'] = 0;

Variable Scope in Functions in PHP:

The scope of a variable is determined based on the context in which is defined. i.e. local or global. In PHP global variables must be declared global inside a function if they are going to be used in that function.

Example: The script below will not produce any result because “x” ‘s scope is outside the function. If the variable is declared as global, it can be used from anywhere in the script.

<?php
$x = 10; //global
Function sample()
{
Echo $x;
}
Test();
?>

Describe $_ENV and $_SERVER:

• $_ENV is the array under Superglobal variables. They are he environment variables. These variables are imported into PHP’s global namespace from the environment of PHP parser.
  Example:
  <?php
  Echo ‘my user name is ‘ .$_ENV[“USER”] ‘!’;
  ?>Output:
  My user name is sample !
• $_SERVER is the array under Superglobal variables. They are array containing information about headers, paths and script locations. Web server creates entries of this array.
  Example:
  <?php
  Echo $_SERVER [‘SERVER_NAME’];
  ?>

About  “this”  Variable:

In order to specify that you are working with local variables within a function $this variable is used. Inside a function of an object, PHP automatically sets the $this variable contains that object – we need not to do anything to have access to it.

Example:

Function person()
{
Print “{$this->age}”;
}

Find the sum of all the multiples of 3 or 5 below 1000.
”
Solution:
“<?php
for($counter=1; $counter < 1000 ; $counter ++)
{
//echo ”

“;
//echo ”
“.$counter.”–> “;

$int_var1 = ($counter/3); //current counter will be divided by 3
$int_var2 = ($counter/5); //current counter will be divided by 5

$str_type1 = gettype($int_var1); //This will return integer if counter was divided by 3 properly
$str_type2 = gettype($int_var2); //This will return integer if counter was divided by 5 properly

if ($str_type1 == ‘integer’ || $str_type2 == ‘integer’ ) //to check which “counter” was properly divided
{
//echo “This is integer”;
$int_result = $int_result+$counter;

}
else
{
//echo ” NON INTEGER” ;
}
}
echo “Result is: $int_result “;

?>
“