How to learn PHP from Scratch.

Posted on: September 22, 2024 in PHP ,

PHP is a widely-used server-side scripting language designed for web development but also used as a general-purpose programming language. PHP scripts are executed on the server, and the result is sent to the browser as plain HTML. Here are the basic concepts:

1. PHP Tags:

PHP code is embedded in HTML using specific opening and closing tags:

PHP

<?php
  // PHP code goes here
?>

Anything between <?php and ?> is treated as PHP code. This allows PHP to be mixed with HTML.

Example of mixing HTML and PHP:

PHP

<html>
<body>
  <h1>Welcome to my website</h1>
  <?php
    echo "Hello, World!";
  ?>
</body>
</html>

2. PHP Variables:

Variables in PHP start with a $ symbol. PHP automatically converts the variable’s type based on its value.

Example:

PHP

<?php
  $name = "Raghu";
  $age = 30;
  echo "My name is $name and I am $age years old.";
?>

PHP Output

  My name is Raghu and I am 30 years old.

3. PHP Data Types:

PHP supports several data types, including:

String: Text data, enclosed in quotes (" " or ' ').
Integer: Whole numbers (e.g., 42).
Float: Decimal numbers (e.g., 3.14).
Boolean: Either true or false.
Array: A collection of values, indexed or associative.
Object: Represents instances of classes.
NULL: A special type that represents a variable with no value.

4. Basic Syntax:

Echo: Used to output data.

PHP

<?php
 echo "Hello, World!";
?>

Comments: Comments can be single-line or multi-line

PHP

<?php
// This is a single-line comment
/* This is a multi-line comment */
?>

5. Control Structures:

If-Else Statements: Basic conditional logic.

PHP

<?php
  $age = 18;
     if ($age >= 18) {
         echo "You are an adult.";
     } else {
         echo "You are a minor.";
     }
?>

Loops: Used for repetitive tasks.

For Loop:

PHP

<?php
  for ($i = 0; $i < 5; $i++) {
    echo "Number: $i<br>";
  }
?>

While Loop:

PHP

<?php
  $i = 0;
  while ($i < 5) {
    echo "Number: $i<?br>";
    $i++;
  }
?>

6. Functions:

Functions allow you to reuse code. You can define your own functions in PHP.

Example:

PHP

<?php
  function greet($name) {
    return "Hello, " . $name;
  }

  echo greet("Raghu");
?>

7. Arrays:

Indexed Arrays:

PHP

<?php
 $fruits = array("Apple", "Banana", "Orange");
  echo $fruits[1]; // Outputs: Banana
?>

Associative Arrays:

PHP

<?php
 $person = array("name" => "John", "age" => 30);
  echo $person['name']; // Outputs: John
?>

8. Form Handling:

PHP is often used to collect form data. The $_POST and $_GET superglobals are used to retrieve form input.

Example:

HTML

<form method="post" action="process.php">
  Name: <input type="text" name="name">
  <input type="submit">
</form>

In process.php:

PHP

<?php
  $name = $_POST['name'];
  echo "Hello, $name";
?>

9. PHP and MySQL:

PHP can be used to connect to databases like MySQL. Here’s a basic example of connecting to a MySQL database and retrieving data:

PHP

<?php
   $conn = new mysqli("localhost", "username", "password", "database");

  if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
  }

  $sql = "SELECT * FROM users";
  $result = $conn->query($sql);

  if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
      echo "Name: " . $row["name"] . "
";
    }
  } else {
    echo "0 results";
  }

  $conn->close();
?>

10. Error Handling:

PHP provides several ways to handle errors. The die() function is often used to stop script execution if something goes wrong.

Example:

PHP

<?php
   $file = fopen("test.txt", "r") or die("Unable to open file!");
  // Do something with the file
?>

Conclusion:

PHP is a flexible and powerful language for building web applications. By mixing PHP with HTML, you can dynamically generate content and interact with databases, making your website interactive.

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