Day 25 – PHP Basics (Beginner Guide for Bug Hunters)

🐘 Day 25: PHP Basics

Aaj hum seekhenge PHP kya hota hai aur kaise kaam karta hai. Bug hunting me backend samajhna bahut zaruri hota hai, aur PHP duniya ki sabse popular server-side languages me se ek hai.

Bahut sari websites PHP par bani hui hain jaise:

  • Facebook (initial version PHP me bana tha)

  • Wikipedia

  • WordPress (Most popular CMS)

Agar aapko web vulnerabilities samajhni hai (SQL Injection, File Upload Bug, etc.), to PHP ki basic knowledge zaruri hai.

🧠 PHP Kya Hai?

PHP (Hypertext Preprocessor) ek server-side scripting language hai.

👉 Server-side ka matlab:
Code server par run hota hai, browser me sirf output dikhai deta hai.

Example:
User form fill karta hai → Data server par jata hai → PHP process karta hai → Result browser me show hota hai.

⚙ PHP Kaise Kaam Karta Hai?

  1. User browser me request bhejta hai

  2. Request server tak jati hai

  3. Server PHP file run karta hai

  4. Output HTML me convert hota hai

  5. Browser ko final result milta hai

PHP file ka extension hota hai:

.php

📝 Basic PHP Syntax

PHP code hamesha start hota hai:

<?php
   // PHP code yaha likha jata hai
?>

Example:

<?php
echo "Hello Alok!";
?>

👉 echo ka use output print karne ke liye hota hai.

📦 PHP Variables

Variables ka use data store karne ke liye hota hai.

PHP me variable $ sign se start hota hai.

<?php
$name = "Alok";
$age = 20;

echo $name;
?>

Important Rules:

  • Variable $ se start hoga

  • Case sensitive hota hai ($name ≠ $Name)

🔢 PHP Data Types

  1. String

  2. Integer

  3. Float

  4. Boolean

  5. Array

Example:

<?php
$x = 100;        // Integer
$y = "Bug Hunt"; // String
?>

🔄 PHP Operators

Arithmetic Operators:

  • +

  • -

  • *

  • /

<?php
$a = 10;
$b = 5;
echo $a + $b;
?>

🔀 If Else Condition

<?php
$age = 18;

if($age >= 18){
   echo "You can vote";
} else {
   echo "You cannot vote";
}
?>

Bug hunting me conditions samajhna important hota hai, kyunki authorization bugs yahi se related hote hain.

📋 PHP Forms Handling

HTML form ka data PHP receive karta hai.

Example:

HTML Form:

<form method="POST">
   <input type="text" name="username">
   <input type="submit">
</form>

PHP:

<?php
$username = $_POST['username'];
echo $username;
?>

⚠ Yahi jagah hoti hai jahan SQL Injection ya XSS bugs milte hain agar input properly validate na ho.

🔐 PHP & Database Connection (Basic Idea)

PHP MySQL database se connect ho sakta hai.

$conn = mysqli_connect("localhost","root","","testdb");

Agar developer input sanitize nahi kare, to SQL Injection vulnerability aa sakti hai.

🎯 Bug Hunting Me PHP Kyu Important?

✔ Server-side logic samajhne ke liye
✔ Authentication & Authorization flaws samajhne ke liye
✔ File upload bugs identify karne ke liye
✔ SQL Injection samajhne ke liye

Agar aapko backend samajh me aata hai, to vulnerability find karna easy ho jata hai.

📝 Practice Task

  1. XAMPP install karo

  2. Ek simple PHP file banao

  3. Echo statement run karo

  4. Ek form banao aur data print karo

🔁 Revision Points

  • PHP server-side language hai

  • $ se variable start hota hai

  • echo output print karta hai

  • Forms data $_POST aur $_GET se milta hai

  • Database connection possible hai

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