HTML5 and PHP: Syntax, Semantics, and Superglobal Variables

Posted on Apr 1, 2025 in Computers

HTML: Markup to differentiate information about content. W3C recommendations for contents and elements. XHTML requires empty elements terminated by a trailing slash. In HTML5, the trailing slash in empty elements is optional. Semantic advantages include maintainability, performance, accessibility, and Search Engine Optimization. HTML5 does not require the use of the <html>, <head>, and <body> tags.

PHP

PHP code is enclosed within <?php ?> tags.

Comments:

  • #
  • /* */
  • //

Variables:

Variables are prefixed with $. Types include boolean, integer, float, string, array, and object.

Constants:

Constants are defined using define(_, _).

String Concatenation:

Strings are appended using . (dot).

Control Structures:

  • if else if else
  • switch() case x:

Functions:

Functions are defined as function name(): string {}. Functions can have default values. Parameters can be passed by reference using &. By default, variables have function scope. Variables in the main scope cannot be accessed within functions unless declared as global.

Arrays:

Arrays can be defined using array(,,,) or [,,,]. All arrays are associative (0=>x, 1=>y). Other keys can also be used.

Iterating Through Arrays:

  • Iterating through values: foreach ($forecast as $value){}
  • Iterating through keys and values: foreach ($forecast as $key => $value)

Superglobal Variables:

  • $GLOBALS: Array for storing data that needs superglobal scope
  • $_COOKIES: Array of cookie data passed to page via HTTP request
  • $_ENV: Array of server environment data
  • $_FILES: Array of file items uploaded to the server
  • $_GET: Array of query string data passed to the server via the URL
  • $_POST: Array of query string data passed to the server via the HTTP header
  • $_REQUEST: Array containing the contents of $_GET, $_POST, and $_COOKIES
  • $_SESSION: Array that contains session data
  • $_SERVER: Array containing information about the request and the server

Example:

if ($_SERVER["REQUEST_METHOD"] == "POST") { if ( isset($_POST["uname"]) … }

HTML: Markup to differentiate information about content. W3C recommendations for contents and elements. XHTML requires empty elements terminated by a trailing slash. In HTML5, the trailing slash in empty elements is optional. Semantic advantages include maintainability, performance, accessibility, and Search Engine Optimization. HTML5 does not require the use of the <html>, <head>, and <body> tags.

PHP

PHP code is enclosed within <?php ?> tags.

Comments:

  • #
  • /* */
  • //

Variables:

Variables are prefixed with $. Types include boolean, integer, float, string, array, and object.

Constants:

Constants are defined using define(_, _).

String Concatenation:

Strings are appended using . (dot).

Control Structures:

  • if else if else
  • switch() case x:

Functions:

Functions are defined as function name(): string {}. Functions can have default values. Parameters can be passed by reference using &. By default, variables have function scope. Variables in the main scope cannot be accessed within functions unless declared as global.

Arrays:

Arrays can be defined using array(,,,) or [,,,]. All arrays are associative (0=>x, 1=>y). Other keys can also be used.

Iterating Through Arrays:

  • Iterating through values: foreach ($forecast as $value){}
  • Iterating through keys and values: foreach ($forecast as $key => $value)

Superglobal Variables:

  • $GLOBALS: Array for storing data that needs superglobal scope
  • $_COOKIES: Array of cookie data passed to page via HTTP request
  • $_ENV: Array of server environment data
  • $_FILES: Array of file items uploaded to the server
  • $_GET: Array of query string data passed to the server via the URL
  • $_POST: Array of query string data passed to the server via the HTTP header
  • $_REQUEST: Array containing the contents of $_GET, $_POST, and $_COOKIES
  • $_SESSION: Array that contains session data
  • $_SERVER: Array containing information about the request and the server

Example:

if ($_SERVER["REQUEST_METHOD"] == "POST") { if ( isset($_POST["uname"]) … }

HTML: Markup to differentiate information about content. W3C recommendations for contents and elements. XHTML requires empty elements terminated by a trailing slash. In HTML5, the trailing slash in empty elements is optional. Semantic advantages include maintainability, performance, accessibility, and Search Engine Optimization. HTML5 does not require the use of the <html>, <head>, and <body> tags.

PHP

PHP code is enclosed within <?php ?> tags.

Comments:

  • #
  • /* */
  • //

Variables:

Variables are prefixed with $. Types include boolean, integer, float, string, array, and object.

Constants:

Constants are defined using define(_, _).

String Concatenation:

Strings are appended using . (dot).

Control Structures:

  • if else if else
  • switch() case x:

Functions:

Functions are defined as function name(): string {}. Functions can have default values. Parameters can be passed by reference using &. By default, variables have function scope. Variables in the main scope cannot be accessed within functions unless declared as global.

Arrays:

Arrays can be defined using array(,,,) or [,,,]. All arrays are associative (0=>x, 1=>y). Other keys can also be used.

Iterating Through Arrays:

  • Iterating through values: foreach ($forecast as $value){}
  • Iterating through keys and values: foreach ($forecast as $key => $value)

Superglobal Variables:

  • $GLOBALS: Array for storing data that needs superglobal scope
  • $_COOKIES: Array of cookie data passed to page via HTTP request
  • $_ENV: Array of server environment data
  • $_FILES: Array of file items uploaded to the server
  • $_GET: Array of query string data passed to the server via the URL
  • $_POST: Array of query string data passed to the server via the HTTP header
  • $_REQUEST: Array containing the contents of $_GET, $_POST, and $_COOKIES
  • $_SESSION: Array that contains session data
  • $_SERVER: Array containing information about the request and the server

Example:

if ($_SERVER["REQUEST_METHOD"] == "POST") { if ( isset($_POST["uname"]) … }

HTML: Markup to differentiate information about content. W3C recommendations for contents and elements. XHTML requires empty elements terminated by a trailing slash. In HTML5, the trailing slash in empty elements is optional. Semantic advantages include maintainability, performance, accessibility, and Search Engine Optimization. HTML5 does not require the use of the <html>, <head>, and <body> tags.

PHP

PHP code is enclosed within <?php ?> tags.

Comments:

  • #
  • /* */
  • //

Variables:

Variables are prefixed with $. Types include boolean, integer, float, string, array, and object.

Constants:

Constants are defined using define(_, _).

String Concatenation:

Strings are appended using . (dot).

Control Structures:

  • if else if else
  • switch() case x:

Functions:

Functions are defined as function name(): string {}. Functions can have default values. Parameters can be passed by reference using &. By default, variables have function scope. Variables in the main scope cannot be accessed within functions unless declared as global.

Arrays:

Arrays can be defined using array(,,,) or [,,,]. All arrays are associative (0=>x, 1=>y). Other keys can also be used.

Iterating Through Arrays:

  • Iterating through values: foreach ($forecast as $value){}
  • Iterating through keys and values: foreach ($forecast as $key => $value)

Superglobal Variables:

  • $GLOBALS: Array for storing data that needs superglobal scope
  • $_COOKIES: Array of cookie data passed to page via HTTP request
  • $_ENV: Array of server environment data
  • $_FILES: Array of file items uploaded to the server
  • $_GET: Array of query string data passed to the server via the URL
  • $_POST: Array of query string data passed to the server via the HTTP header
  • $_REQUEST: Array containing the contents of $_GET, $_POST, and $_COOKIES
  • $_SESSION: Array that contains session data
  • $_SERVER: Array containing information about the request and the server

Example:

if ($_SERVER["REQUEST_METHOD"] == "POST") { if ( isset($_POST["uname"]) … }