Server Side Scripting, PHP Variables, and Loops

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Part A: Server Side Scripting

Server side scripting is a technique where scripts are executed on the web server, and the resulting output (usually HTML) is sent to the client's browser.

• The user cannot see the source code; only the processed output is visible
• The server processes the script, interacts with databases, performs logic, and generates dynamic web pages
• Examples of server side scripting languages: PHP, Python, ASP.NET, Node.js, Java (JSP)

How it works:

• Client sends a request to the server (e.g., requesting a .php page)
• The web server identifies the script and passes it to the PHP interpreter
• The interpreter executes the code and returns HTML output
• The server sends this HTML response back to the client browser

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Part B: Defining and Declaring Variables in PHP

In PHP, a variable is declared using the dollar sign ($) followed by the variable name. PHP is a loosely typed language, so no data type declaration is needed.

Rules for declaring variables:

• A variable starts with $ followed by the name (e.g., $name)
• Variable name must start with a letter or underscore (not a number)
• Variable names are case-sensitive ($Age and $age are different)
• No need to declare data type — PHP automatically assigns it

Example:

<?php
  $name = "John";        // String variable
  $age = 25;             // Integer variable
  $price = 99.5;         // Float variable
  $is_active = true;     // Boolean variable

  echo $name;
  echo $age;
?>

Variable Scopes in PHP:

• Local – declared inside a function, accessible only within that function
• Global – declared outside a function, accessible outside but not inside functions (unless using global keyword)
• Static – retains its value even after the function execution ends

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Part C: While Loop in PHP

The while loop executes a block of code as long as the specified condition is true. It is an entry-controlled loop (condition is checked before execution).

Syntax:

while (condition) {
    // code to execute
}

Program: Print numbers 1 to 5 using while loop

<?php
  $i = 1;
  while ($i <= 5) {
      echo "Number: " . $i . "<br>";
      $i++;
  }
?>

Output:

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

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Part D: Do-While Loop in PHP

The do-while loop executes the block of code at least once, and then repeats as long as the condition is true. It is an exit-controlled loop (condition is checked after execution).

Syntax:

do {
    // code to execute
} while (condition);

Program: Print numbers 1 to 5 using do-while loop

<?php
  $i = 1;
  do {
      echo "Number: " . $i . "<br>";
      $i++;
  } while ($i <= 5);
?>

Output:

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

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Key Difference: While vs Do-While

Feature	While Loop	Do-While Loop
Type	Entry-controlled	Exit-controlled
Minimum execution	0 times (if condition is false initially)	At least 1 time
Condition check	Before the loop body	After the loop body

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Conclusion: Server side scripting enables dynamic web content generation. PHP provides simple variable declaration using $ and supports both while (entry-controlled) and do-while (exit-controlled) loops for repetitive tasks.