How to declare variables?

In PHP, declaring variables is a fundamental concept that allows you to store and manipulate data. Here’s how you can declare variables in PHP:

1. Variable Naming Rules:

   – Variable names in PHP must start with a dollar sign `$` followed by a letter or underscore.

   – Variable names can contain letters, numbers, and underscores.

   – Variable names are case-sensitive, meaning `$myVar` and `$myvar` are treated as different variables.

   – Avoid using PHP reserved words (e.g., `echo`, `if`, `while`) as variable names.

2. Variable Assignment:

   – To declare a variable in PHP, you simply assign a value to it using the assignment operator (`=`). For example:

   
```php
$name = "John";
$age = 30;
```

3. Data Types:

   – PHP is a loosely typed language, meaning you don’t need to specify the data type of a variable explicitly. PHP will determine the data type based on the value assigned to it. Common data types in PHP include strings, integers, floating-point numbers, booleans, arrays, and objects.

4. Concatenation:

   – You can concatenate (combine) variables and strings using the period (`.`) operator. For example:

```php
$firstName = "John";
$lastName = "Doe";
$fullName = $firstName . " " . $lastName;
```

5. Printing Variables:

   – To display the value of a variable, you can use the `echo` or `print` statement. For instance:

```php
$message = "Hello, World!";
echo $message;
```

6. Variable Scope:

   – PHP variables have different scopes, such as global, local, and static. Variables declared outside functions or code blocks have global scope, while those declared within functions have local scope. You can use the `global` keyword to access global variables from within a function.

7. Variable Interpolation:

   – In double-quoted strings, you can directly interpolate variables by enclosing them in curly braces `{}`. For example:

```php
$name = "Alice";
echo "Hello, {$name}!";
```

That’s a basic overview of declaring variables in PHP. Understanding these concepts is crucial for effectively working with data in PHP scripts and building dynamic web applications.