PHP Syntax

Basic PHP Syntax & Document Structure

PHP scripts are plain text files saved with the .php extension. PHP code is enclosed within opening <?php tags and closing ?> tags.

PHP Parsing & Delimiters

When the web server passes a file to the PHP parser, it evaluates code inside <?php ... ?> tags and leaves everything outside untouched as raw content.

<?php
// Standard PHP opening tag
$title = "Mastering PHP Syntax";
// Closing tag is required if file mixes HTML and PHP
?>
<h1><?= $title ?></h1>
<?php
// If a file contains ONLY PHP code, omit the closing tag!

flowchart LR
    A["Raw HTML Text"] --> B["Parser Passes Through Directly"]
    C["<?php Code Block ?>"] --> D["Parser Executes Logic"]
    D --> E["Appends Result Output to Response"]
    B --> E

Core Syntax Rules

1. Statements End with Semicolons ;: Every individual PHP statement must end with a semicolon.
2. Case Sensitivity Rules:
   • Case-Insensitive: Function names, class names, keywords (if, else, echo, while) are case-insensitive.
   • Case-Sensitive: Variable names ($name vs $Name) are strictly case-sensitive!
3. Closing Tags in Pure PHP Files: Omitting ?> at the end of pure PHP files prevents accidental trailing whitespace or header errors.

Practical Code Example

<?php
declare(strict_types=1);

// Variable declarations (Case-Sensitive)
$userName = "Maksudur";
$username = "Guest"; // Different variable!

// Keyword case insensitivity (Convention is lowercase)
ECHO "Hello, " . $userName . "!
";
echo "Hello, " . $username . "!
";

// Semicolons terminate statements
$totalAmount = 150.00;
$discount = 15.00;
$finalPrice = $totalAmount - $discount;

echo "Final Payable Price: $" . number_format($finalPrice, 2);

Best Practices

• Follow PSR-12 Coding Standards: Write PHP keywords and function calls in lowercase (echo, foreach, function).
• Omit ?> on Pure PHP Files: Avoid unexpected whitespace buffer output at the end of class or config files.
• Enforce Strict Types: Place declare(strict_types=1); at the very top of PHP files for scalar type safety.

Self-Check Challenge

Write a PHP script that declares two variables $firstName and $lastName, concatenates them into $fullName, and prints $fullName using echo!