Mastering PHP: From Basics to Building Dynamic Web Applications

Chapter 3: Variables, Data Types & Control Flow

🔹 1. Introduction

Now that you’ve set up your PHP environment and learned basic syntax, it’s time to learn how to store, process, and control data using PHP.

This chapter will walk you through:

• Declaring and using variables
• Understanding PHP's dynamic data types
• Using operators for computation and logic
• Writing conditions and control structures
• Looping through data

🔹 2. Variables in PHP

A variable in PHP is a container used to store data — like numbers, strings, arrays, etc.

✅ Syntax:

$variableName = value;

✅ Example:

$name = "Alice";

$age = 28;

$price = 99.99;

✅ PHP variables:

• Start with $
• Are case-sensitive
• Must begin with a letter or underscore

🔹 3. Data Types in PHP

PHP is loosely typed, meaning variables can change types automatically.

✅ Primary Data Types:

✅ Use var_dump($variable) to check the value and type of a variable.

🔹 4. Operators in PHP

✅ Arithmetic Operators:

$a = 10;

$b = 2;

echo $a + $b; // 12

✅ Assignment Operators:

$x = 10;

$x += 5;  // $x is now 15

✅ Comparison Operators:

$a == $b; // equal

$a != $b; // not equal

$a > $b;  // greater than

✅ Logical Operators:

$a && $b; // and

$a || $b; // or

!$a;      // not

🔹 5. Conditional Statements

✅ if, else, elseif:

$score = 75;

if($score >= 90){

  echo "A grade";

} elseif($score >= 75){

  echo "B grade";

} else {

  echo "C grade";

}

✅ switch:

$role = "admin";

switch($role){

  case "admin":

    echo "Welcome Admin!";

    break;

  case "editor":

    echo "Welcome Editor!";

    break;

  default:

    echo "Unknown role.";

}

✅ Use switch when checking one variable against many values.

🔹 6. Loops in PHP

✅ for Loop:

for($i = 0; $i < 5; $i++){

  echo "Line $i<br>";

}

✅ while Loop:

$i = 0;

while($i < 5){

  echo "$i ";

  $i++;

}

✅ do...while Loop:

$i = 0;

do {

  echo "$i ";

  $i++;

} while($i < 5);

✅ foreach Loop (Best for Arrays):

$fruits = ["Apple", "Banana", "Mango"];

foreach($fruits as $fruit){

  echo "$fruit<br>";

}

🔹 7. Break and Continue

✅ break:

for($i = 0; $i < 10; $i++){

  if($i == 5) break;

  echo "$i ";

}

✅ continue:

for($i = 0; $i < 10; $i++){

  if($i == 5) continue;

  echo "$i ";

}

✅ Summary Table: Chapter 2