PHP Complete Tutorial – Learn PHP from Scratch | Esikhcha

🐘 PHP Complete Tutorial

From basic syntax to form validation — everything you need to master PHP

📖 Syntax & Variables 🔄 Loops & Functions 📦 Arrays & Superglobals 🔍 Regular Expressions 📝 Form Handling

CHAPTER 1

PHP Intro & Installation

PHP (Hypertext Preprocessor) is a widely-used, open-source server-side scripting language designed for web development. It runs on servers like Apache, Nginx, and IIS.

To run PHP, you need a local server environment like XAMPP, WAMP, MAMP or a web hosting service. PHP files have the extension .php and can contain HTML, CSS, JavaScript, and PHP code.

💡 PHP code is executed on the server, and the result is sent to the browser as plain HTML.

CHAPTER 2

PHP Syntax & Comments

PHP code is embedded in HTML using <?php ... ?> tags.

▶ Basic PHP File

<!DOCTYPE html>
<html>
<body>
<?php
  // This is a single-line comment
  echo "Hello, World!";  // Outputs text
  
  # This is also a single-line comment
  
  /*
    This is a
    multi-line comment
  */
?>
</body>
</html>

Output: Hello, World!

CHAPTER 3

Variables, Echo & Print

Variables in PHP start with $ followed by the variable name. They are case-sensitive and dynamically typed.

<?php
  $name = "John";        // string
  $age = 25;             // integer
  $price = 19.99;        // float
  $is_admin = true;      // boolean
  
  // echo (no return value)
  echo "Hello $name";
  echo "Age: " . $age;
  
  // print (returns 1, slightly slower)
  print "Welcome!";
  
  // print_r (for arrays)
  print_r([1, 2, 3]);
?>

Hello John
Age: 25
Welcome!
Array ( [0] => 1 [1] => 2 [2] => 3 )

CHAPTER 4

Data Types & Type Casting

PHP supports: string, integer, float, boolean, array, object, NULL, resource.

<?php
  $x = "Hello";          // string
  $y = 42;               // integer
  $z = 3.14;             // float
  $a = true;             // boolean
  $b = null;             // NULL
  
  // Type casting
  $num = "123";
  $int_num = (int)$num;      // 123
  $float_num = (float)$num;  // 123.0
  $str_num = (string)456;    // "456"
  
  // Check type
  var_dump($x);   // string(5) "Hello"
?>

CHAPTER 5

Strings & Numbers

<?php
  // String functions
  $text = "Hello PHP World";
  echo strlen($text);           // 16
  echo str_word_count($text);   // 3
  echo strpos($text, "PHP");    // 6
  echo str_replace("World", "Everyone", $text);
  
  // Number functions
  echo is_numeric("123");       // true
  echo number_format(1234.56, 2);  // 1,234.56
  echo rand(1, 100);            // random number
?>

CHAPTER 6

Math Functions & Constants

<?php
  echo pi();           // 3.1415926535898
  echo min(2,4,6,1);   // 1
  echo max(2,4,6,1);   // 6
  echo abs(-7);        // 7
  echo sqrt(64);       // 8
  echo round(3.6);     // 4
  
  // Define constants
  define("SITE_NAME", "ReadersNepal");
  const VERSION = "1.0";
  echo SITE_NAME;      // ReadersNepal
?>

CHAPTER 7

Magic Constants

Magic constants change depending on where they are used.

<?php
  echo __LINE__;        // Current line number
  echo __FILE__;        // Full file path
  echo __DIR__;         // Directory path
  echo __FUNCTION__;    // Function name
  echo __CLASS__;       // Class name
  echo __METHOD__;      // Method name
  echo __NAMESPACE__;   // Namespace name
?>

CHAPTER 8

PHP Operators

Type	Operators	Example
Arithmetic	+ – * / % **	$a + $b
Assignment	= += -= *= /=	$x += 5
Comparison	== === != !== > < >= <=	$a === $b
Logical	and or xor && \|\| !	$a && $b
String	. .=	$a . $b

<?php
  $a = 10; $b = 3;
  echo $a + $b;     // 13
  echo $a . $b;     // "103"
  echo $a == "10";  // true (value)
  echo $a === "10"; // false (type)
?>

CHAPTER 9

If/Else, Switch, Match

<?php
  // If/Else
  $score = 85;
  if ($score >= 90) {
    echo "A";
  } elseif ($score >= 80) {
    echo "B";   // Output: B
  } else {
    echo "C";
  }
  
  // Switch
  $day = "Monday";
  switch ($day) {
    case "Monday": echo "Start of week"; break;
    case "Friday": echo "Weekend coming"; break;
    default: echo "Mid week";
  }
  
  // Match (PHP 8.0+)
  $status = match($score) {
    default => "Valid"
  };
?>

CHAPTER 10

Loops: for, while, do-while, foreach

<?php
  // for loop
  for ($i = 1; $i <= 5; $i++) {
    echo $i . " ";   // 1 2 3 4 5
  }
  
  // while loop
  $j = 1;
  while ($j <= 3) {
    echo $j; $j++;
  }
  
  // foreach (for arrays)
  $colors = ["red", "green", "blue"];
  foreach ($colors as $color) {
    echo $color;
  }
  
  // foreach with key
  $ages = ["John" => 25, "Jane" => 30];
  foreach ($ages as $name => $age) {
    echo "$name is $age";
  }
?>

CHAPTER 11

Functions

<?php
  // Basic function
  function greet($name) {
    return "Hello, $name!";
  }
  echo greet("Alice");
  
  // Default parameters
  function multiply($a, $b = 2) {
    return $a * $b;
  }
  echo multiply(5);   // 10
  
  // Variable scope
  $global_var = 10;
  function test() {
    global $global_var;
    $local_var = 5;
    return $global_var + $local_var;
  }
  
  // Anonymous function
  $square = function($x) { return $x * $x; };
  echo $square(4);  // 16
?>

CHAPTER 12

Arrays: Indexed, Associative, Multidimensional

<?php
  // Indexed array
  $fruits = ["Apple", "Banana", "Orange"];
  echo $fruits[0];           // Apple
  
  // Associative array (key/value)
  $person = ["name" => "John", "age" => 30, "city" => "NYC"];
  echo $person["name"];      // John
  
  // Multidimensional array
  $matrix = [
    [1, 2, 3],
    [4, 5, 6]
  ];
  echo $matrix[1][2];        // 6
  
  // Array functions
  echo count($fruits);       // 3
  array_push($fruits, "Mango");
  sort($fruits);
?>

CHAPTER 13

Superglobals ($_GET, $_POST, $_SERVER, $_SESSION, $_COOKIE)

<?php
  // $_GET - data from URL query string
  // example.com/page.php?name=John
  $name = $_GET['name'] ?? 'Guest';
  
  // $_POST - data from HTML forms (method="POST")
  $email = $_POST['email'] ?? '';
  
  // $_SERVER - server info
  echo $_SERVER['REQUEST_METHOD'];  // GET/POST
  echo $_SERVER['REMOTE_ADDR'];     // Client IP
  
  // $_SESSION - persistent data across pages
  session_start();
  $_SESSION['user_id'] = 123;
  
  // $_COOKIE - browser cookies
  setcookie("theme", "dark", time() + 86400);
  echo $_COOKIE['theme'] ?? 'light';
?>

⚠️ Always validate and sanitize superglobal data for security!

CHAPTER 14

Regular Expressions (RegEx)

preg_match() – checks if pattern matches
preg_replace() – replaces pattern matches
preg_split() – splits string by pattern

<?php
  // Email validation
  $email = "user@example.com";
  if (preg_match("/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/", $email)) {
    echo "Valid email";
  }
  
  // Phone number (US format)
  $phone = "123-456-7890";
  if (preg_match("/^\d{3}-\d{3}-\d{4}$/", $phone)) {
    echo "Valid phone";
  }
  
  // Replace digits with X
  $text = "My number is 12345";
  $result = preg_replace("/\d/", "X", $text);
  echo $result;  // "My number is XXXXX"
  
  // Split string
  $tags = "apple,banana,orange";
  $arr = preg_split("/,/", $tags);  // ['apple', 'banana', 'orange']
?>

CHAPTER 15

Form Handling & Validation

Complete example with validation for required fields, email, and URL.

📝 HTML Form

<form method="POST" action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']); ?>">
  Name: <input type="text" name="name"><br>
  Email: <input type="text" name="email"><br>
  Website: <input type="text" name="website"><br>
  <input type="submit" name="submit" value="Submit">
</form>

✅ PHP Validation Logic

<?php
  $name = $email = $website = "";
  $nameErr = $emailErr = $websiteErr = "";
  
  if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Required field validation
    if (empty($_POST["name"])) {
      $nameErr = "Name is required";
    } else {
      $name = test_input($_POST["name"]);
      if (!preg_match("/^[a-zA-Z-' ]*$/", $name)) {
        $nameErr = "Only letters and spaces allowed";
      }
    }
    
    // Email validation
    if (empty($_POST["email"])) {
      $emailErr = "Email is required";
    } else {
      $email = test_input($_POST["email"]);
      if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $emailErr = "Invalid email format";
      }
    }
    
    // URL validation
    if (!empty($_POST["website"])) {
      $website = test_input($_POST["website"]);
      if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i", $website)) {
        $websiteErr = "Invalid URL";
      }
    }
  }
  
  function test_input($data) {
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
  }
?>

CHAPTER 16

Complete Form with Validation

🎯 Full Registration Form Example

<?php
  // Initialize variables
  $name = $email = $gender = $comment = "";
  $nameErr = $emailErr = $genderErr = "";
  $success = false;
  
  if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $isValid = true;
    
    // Validate Name
    if (empty($_POST["name"])) {
      $nameErr = "Name is required";
      $isValid = false;
    } else {
      $name = test_input($_POST["name"]);
    }
    
    // Validate Email
    if (empty($_POST["email"])) {
      $emailErr = "Email is required";
      $isValid = false;
    } else {
      $email = test_input($_POST["email"]);
      if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $emailErr = "Invalid email format";
        $isValid = false;
      }
    }
    
    // Validate Gender
    if (empty($_POST["gender"])) {
      $genderErr = "Gender is required";
      $isValid = false;
    } else {
      $gender = test_input($_POST["gender"]);
    }
    
    $comment = test_input($_POST["comment"] ?? "");
    
    if ($isValid) {
      $success = true;
    }
  }
  
  function test_input($data) {
    return htmlspecialchars(stripslashes(trim($data)));
  }
?>

<?php if ($success): ?>
  <div style="background: #dcfce7; padding: 1rem; border-radius: 8px;">
    ✅ Form submitted successfully!<br>
    Name: <?php echo $name; ?><br>
    Email: <?php echo $email; ?><br>
    Gender: <?php echo $gender; ?><br>
    Comment: <?php echo $comment; ?>
  </div>
<?php endif; ?>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>">
  <label>Name: *</label>
  <input type="text" name="name" value="<?php echo $name; ?>">
  <span style="color:red;"><?php echo $nameErr; ?></span><br>
  
  <label>Email: *</label>
  <input type="text" name="email" value="<?php echo $email; ?>">
  <span style="color:red;"><?php echo $emailErr; ?></span><br>
  
  <label>Gender: *</label>
  <input type="radio" name="gender" value="female" <?php if ($gender=="female") echo "checked"; ?>> Female
  <input type="radio" name="gender" value="male" <?php if ($gender=="male") echo "checked"; ?>> Male
  <span style="color:red;"><?php echo $genderErr; ?></span><br>
  
  <label>Comment:</label>
  <textarea name="comment"><?php echo $comment; ?></textarea><br>
  
  <input type="submit" name="submit" value="Submit">
</form>

🔒 This example includes: required field validation, email format validation, XSS prevention (htmlspecialchars), and data persistence after submission.

SUMMARY

🎯 What You’ve Learned

PHP syntax, variables, data types, and operators
Conditional statements (if/else, switch, match)
Loops (for, while, foreach)
Functions (built-in and user-defined)
Arrays (indexed, associative, multidimensional)
Superglobals ($_GET, $_POST, $_SESSION, $_SERVER, $_COOKIE)
Regular expressions for pattern matching
Complete form handling with validation

💡 Next steps: Practice building real applications like contact forms, login systems, and CRUD operations with databases.