Variable declare in PHP

Declaring (Creating) PHP Variables
  • Variables are "containers" for storing information.
  • In PHP, a variable starts with the $ sign, followed by the name of the variable. 
    • <!DOCTYPE html>
<html>
<body>

<?php
$hlo = "Hello PHP coders!";
$a = 10;
$b = 20.5;

echo $hlo;
echo "<br>";
echo $a;
echo "<br>";
echo $b;
?>

</body>
</html>

    Note: When you assign a text value to a variable, put quotes around the value.

    Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it.

  • In a PHP variables name like $a, $b, $name, $total_products, $bikename.
PHP variables Rules
  • A variable name cannot start with a number.
  • A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ).
  • A variable name must start with a letter or the underscore character.
  • Variable names are case-sensitive ($name and $NAME are two different variables.
  • A variable starts with the $ sign.
PHP variables execute
  • The PHP echo statement is often used to output data.
    • <!DOCTYPE html>
<html>
<body>

<?php
$hello = "PHP Coders";
echo "Hello $hello!";

echo "<br/>";
$hello = "PHP Coders";
echo "Hello " . $hello . "!";

echo "<br/>";
$a = 5;
$b = 4;
echo $a + $b;

?>

</body>
</html>
PHP Variables Scope
  • In PHP, declared PHP anywhere in the webpage so variables can be declared anywhere in the webpage.
  • The scope of a variable is the part of the script where the variable can be used.
  • PHP has three types of a declared variable.
    • Local
    • Global
    • Static
  • Example
  • 1.Local Variable

    • The variables that are declared in a function are called local variables for that function, so outside of the function that variable is not used, it will show error - Undefined variable.

    • 1. A local variable declared in function example.
      • <!DOCTYPE html>
<html>
<body>

<?php
function loc_var()
{
$ab = 2;
echo "Local variable 'ab' is : $ab";
} loc_var();
?>

</body>
</html>
    • 2. A local variable declared out of function example.
      • <!DOCTYPE html>
<html>
<body>

<?php
function loc_var()
{
$ab = 2;
echo "Local variable 'ab' is : $ab";
}
loc_var();
echo "Local variable out of function 'ab' is : $ab";
?>

</body>
</html>

      Output:

      Local variable 'a' is : 2
      Notice: Undefined variable: ab in C:\xampp\htdocs\example\p4.php on line 13
      Local variable out of function 'ab' is :
  • 2.Global variable

    • The global keyword is used to access a global variable from within a function

  • 1. A global variable declared, defined in function example.
    • <!DOCTYPE html>
<html>
<body>

<?php
$var_name = "php coders point";
function glob_var()
{
global $var_name;
echo "Variable in the function: ". $var_name;
echo "</br>";
}
glob_var();
echo "Variable outside of the function: ". $var_name;
?>

</body>
</html>
  • 2. A global variable declared, not declared in function example.
    • <!DOCTYPE html>
<html>
<body>

<?php
$var_name = "php coders point";
function glob_var()
{
echo "Variable in the function: ". $var_name;
echo "</br>";
}
glob_var();
echo "Variable outside of the function: ". $var_name;
?>

</body>
</html>

    Output:

    Notice: Undefined variable: var_name in C:\xampp\htdocs\example\p5.php on line 9
    Variable in the function:
    Variable outside of the function: php coders point
  • 3. A global variable declared Using $GLOBALS.
    • <!DOCTYPE html>
<html>
<body>

<?php
$number1 = 10;
$number2 = 15;
function glob_var()
{
$mul = $GLOBALS['number1'] * $GLOBALS['number2'];
echo "Multiplication of global variables : " .$mul;
}
glob_var();
?>

</body>
</html>
  • 3. global variable, local variable has higher priority than the global variable.
    • <!DOCTYPE html>
<html>
<body>

<?php
$number1 = 10;
$number2 = 15;
function glob_var()
{
$number1 = 10;
$number2 = 10;

$mul = $number1 * $number2."<br/>";
echo "Multiplication of global variables in a function : " .$mul."<br/>";
}
glob_var();

$mul = $GLOBALS['number1'] * $GLOBALS['number2'];
echo "Multiplication of global variables out of a function: " .$mul;
?>

</body>
</html>
  • 3.Static variable

    • Normally, when a function is executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job.To do this, use the static keyword when you first declare the variable

  • 1. A global variable declared, defined in function example.
    • <!DOCTYPE html>
<html>
<body>

<?php
function stati_var()
{
static $x = 3;
echo $x;
$x--;
}
stati_var();
echo "<br/>";
stati_var();
echo "<br/>";
stati_var();
echo "<br/>";
?>

</body>
</html>
  • Then, each time the function is called, that variable will still have the information it contained from the last time the function was called.

    • Note: The variable is still local to the function.

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