PHP Variable
As PHP is a loosely typed language, so we do not need
to declare the data types of the variables. It automatically analyzes the
values and makes conversions to its correct datatype.
After declaring a variable, it can be reused
throughout the code.
Assignment Operator (=) is used to assign the value to
a variable.
Syntax of declaring a variable in PHP is given below:
$variablename=value;
Rules
for declaring PHP variable:
- A
variable must start with a dollar ($) sign, followed by the variable name.
- It can
only contain alpha-numeric character and underscore (A-z, 0-9, _).
- A
variable name must start with a letter or underscore (_) character.
- A PHP
variable name cannot contain spaces.
- One
thing to be kept in mind that the variable name cannot start with a number
or special symbols.
- PHP
variables are case-sensitive, so $name and $NAME both are treated as
different variable.
PHP Variable: Declaring
string, integer, and float
Variable.php
<?php
$str="hello string";
$x=200;
$y=44.6;
echo "string is: $str <br/>";
echo "integer is: $x <br/>";
echo "float is: $y <br/>";
?>
Output
string
is: hello string
integer
is: 200
float
is: 44.6
PHP Variable: Sum of two variables
<?php
$x=5;
$y=6;
$z=$x+$y;
echo $z;
?>
Output:
11
PHP Variable: case sensitive
In PHP, variable names are case
sensitive. So variable name "color" is different from Color, COLOR,
COLor etc.
<?php
$color="red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>
Output:
My car is red
Notice: Undefined variable: COLOR in
C:\wamp\www\variable.php on line 4
My house is
Notice: Undefined variable: coLOR in
C:\wamp\www\variable.php on line 5
My boat is
PHP: Loosely typed language
PHP is a loosely typed language, it
means PHP automatically converts the variable to its correct data type.
PHP Variable Scope
The scope of a
variable is defined as its range in the program under which it can be accessed.
In other words, "The scope of a variable is the portion of the program
within which it is defined and can be accessed."
PHP has three
types of variable scopes:
- Local
variable
- Global
variable
- Static
variable
Local variable
1. The variables that are
declared within a function are called local variables for that function.
2. These local variables have
their scope only in that particular function in which they are declared. This
means that these variables cannot be accessed outside the function, as they
have local scope.
3. A variable declaration
outside the function with the same name is completely different from the
variable declared inside the function.
4. Example: File:
local_variable1.php
<?php
function local_var()
{
$num = 45; //local variable
echo "Local variable declared inside the function is: ". $num;
}
local_var();
?>
Output:
Local variable declared inside the function is: 45
File: local_variable2.php
<?php
function mytest()
{
$lang = "PHP";
echo "Web development language: " .$lang;
}
mytest();
//using $lang (local variable) outside the function will generate an error
echo $lang;
?>
Output:
Web development language: PHPNotice: Undefined variable: lang in D:\xampp\htdocs\program\p3.php on line 28
Global variable
1. The global variables are
the variables that are declared outside the function.
2. These variables can be
accessed anywhere in the program.
3. To access the global
variable within a function, use the GLOBAL keyword before the variable.
However, these variables can be directly accessed or used outside the function
without any keyword.
4. Therefore there is no need
to use any keyword to access a global variable outside the function.
5. Example: File:
global_variable1.php
<?php
$name = "Sanaya Sharma"; //Global Variable
function global_var()
{
global $name;
echo "Variable inside the function: ". $name;
echo "</br>";
}
global_var();
echo "Variable outside the function: ". $name;
?>
Output:
Variable inside the function: Sanaya SharmaVariable outside the function: Sanaya Sharma
File: global_variable2.php
<?php
$name = "Sanaya Sharma"; //global variable
function global_var()
{
echo "Variable inside the function: ". $name;
echo "</br>";
}
global_var();
?>
Output:
Notice: Undefined variable: name in D:\xampp\htdocs\program\p3.php on line 6Variable inside the function:
Using $GLOBALS instead of
global
1. Another way to use the
global variable inside the function is predefined $GLOBALS array.
2. Example: File: global_variable3.php
<?php
$num1 = 5; //global variable
$num2 = 13; //global variable
function global_var()
{
$sum = $GLOBALS['num1'] + $GLOBALS['num2'];
echo "Sum of global variables is: " .$sum;
}
global_var();
?>
Output:
Sum of global variables is: 18
3. If two variables, local and
global, have the same name, then the local variable has higher priority than
the global variable inside the function.
File: global_variable2.php
<?php
$x = 5;
function mytest()
{
$x = 7;
echo "value of x: " .$x;
}
mytest();
?>
Output:
Value of x: 7
Static variable
1. It is a feature of PHP to
delete the variable, once it completes its execution and memory is freed.
Sometimes we need to store a variable even after completion of function
execution. Therefore, another important feature of variable scoping is static
variable.
2. We use the static keyword
before the variable to define a variable, and this variable is called as static variable.
3. Static variables exist only
in a local function, but it does not free its memory after the program
execution leaves the scope.
4. Example: File:
static_variable.php
<?php
function static_var()
{
static $num1 = 3; //static variable
$num2 = 6; //Non-static variable
//increment in non-static variable
$num1++;
//increment in static variable
$num2++;
echo "Static: " .$num1 ."</br>";
echo "Non-static: " .$num2 ."</br>";
}
//first function call
static_var();
//second function call
static_var();
?>
Output:
Static: 4Non-static: 7Static: 5Non-static: 7
You have to notice that
$num1 regularly increments after each function call, whereas $num2 does not.
This is why because $num1 is not a static variable, so it freed its memory
after the execution of each function call.