PHP Variables

Variables in PHP are used to store data values. In PHP, a variable starts with the dollar sign ($) followed by the name of the variable. Here’s an overview of PHP variables:

Rules for PHP Variables:

1. Variable names must start with a letter or underscore (_) character.
2. Variable names cannot start with a number.
3. Variable names can only contain alphanumeric characters and underscores.
4. Variable names are case-sensitive ($variable is different from $Variable).
5. PHP does not require variable declaration explicitly before using them.

Variable Declaration and Assignment:

• $name = "John"; // Assigning a string value to a variable
$age = 30; // Assigning an integer value to a variable
$height = 5.9; // Assigning a floating-point value to a variable
$isStudent = true; // Assigning a boolean value to a variable

Variable Output:

• echo $name; // Output: John
echo $age; // Output: 30
echo $height; // Output: 5.9
echo $isStudent; // Output: 1 (true value in PHP is displayed as 1)

Variable Scope:

• Local Scope: Variables declared inside a function have local scope and can only be accessed within that function.
• Global Scope: Variables declared outside of any function have global scope and can be accessed from anywhere in the script.

Example of Local and Global Scope:

• $globalVariable = "I am a global variable";
function testScope() {
 $localVariable = "I am a local variable";
 echo $globalVariable; // Error: $globalVariable is not accessible inside the function
 echo $localVariable; // Output: I am a local variable
}
testScope();
echo $globalVariable; // Output: I am a global variable