Variables PHP

• Variables in PHP start with a dollar sign $ followed by the variable name.
• Variable names are case-sensitive and can contain letters, numbers, or underscores.
• Variables must start with a letter or underscore and cannot start with a number.

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$name = "John";
$age = 25;

In this example, $name and $age are two variables. $name stores a string, and $age stores an integer.

You can assign values to variables using the assignment operator =

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$fruit = "apple";
$quantity = 10;
 

In this example, we assigned the string "apple" to the $fruit variable and the integer 10 to the $quantity variable.

• PHP is loosely typed, meaning you don't need to declare the data type of a variable explicitly.
• PHP automatically determines the data type based on the value assigned.

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$name = "John";     // $name is a string
$age = 25;          // $age is an integer
$price = 3.99;      // $price is a float
$isStudent = true;  // $isStudent is a boolean
 

• Variables can have different scopes, such as local and global.
• Variables declared within a function are typically local and not accessible outside that function.
• Global variables are declared outside of any function and can be accessed from anywhere within the script.

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$globalVar = 42; // This is a global variable
function myFunction() {
    $localVar = 10; // This is a local variable
    echo $globalVar; // Accessing a global variable within a function
}
myFunction();
echo $localVar; // This will result in an error; $localVar is not accessible here
 

• You can include variables within double-quoted strings, and PHP will replace them with their values.

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$name = "Alice";
echo "Hello, $name!";
// Output: Hello, Alice!
 

You can concatenate (join) variables and strings using the . operator.

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$first_name = "John";
$last_name = "Doe";
$full_name = $first_name . " " . $last_name;
echo $full_name;
// Output: John Doe
 

Variables are essential in PHP for storing and manipulating data. Understanding how to declare, assign, and use variables is fundamental to writing PHP scripts and building dynamic web applications.