PHP Programming Fundamentals

PHP supports three comment styles: single-line comments using // and #, and multi-line comments using /* */. The syntax <!__ __> is not a valid PHP comment style - it resembles HTML comments but is incorrect for PHP code.

PHP supports multiple tag styles: standard , short tags , and script tags . The ASP-style tags <% %> were supported in older PHP versions with asp_tags enabled but were removed in PHP 7.0, making them the most incorrect option among modern PHP installations.

In PHP, every statement must end with a semicolon (;). This is a fundamental syntax rule that separates statements, similar to other C-style languages like JavaScript and Java.

PHP variables always begin with a dollar sign ($) followed by the variable name. This is a mandatory syntax - variables without $ are treated as constants or barewords, not variables.

PHP is a server-side scripting language that executes on the web server before sending HTML to the client's browser. Unlike JavaScript (client-side), PHP code runs entirely on the server and the browser never sees the PHP source.

The GET method appends form data to the URL as a query string (e.g., page.php?name=value). This data is visible in the browser's address bar and has length limitations (typically 2KB-8KB depending on browser/server).

The POST method sends data in the HTTP request body, not the URL. This allows much larger data transfers (no theoretical limit, practically up to server's post_max_size setting, often 8MB+), making it suitable for file uploads and long forms.

The === operator is the strict equality operator in PHP. It checks both value AND type - '5' === 5 returns false because one is a string and one is an integer. Use == for loose equality (type juggling) or === when type matters.

PHP was originally designed as an Apache module (mod_php) and remains officially integrated with Apache HTTP Server. While PHP can run on other servers (IIS, nginx via FastCGI), Apache has the most native support history.

The dot operator (.) concatenates strings in PHP: $str = 'Hello' . ' World' results in 'Hello World'. The .= operator concatenates and assigns: $str .= '!' appends to $str. Option B is nonsensical PHP syntax.

PHP arrays are created using array() with optional key-value pairs: array('key' => 'value', 'key2' => 'value2'). The => operator associates keys with values. Modern PHP also supports the shorter [] syntax.

func_get_args() returns an array containing all arguments passed to the current function. This is useful for variable-length argument lists. Related functions: func_num_args() returns count, func_get_arg(n) returns single argument at position n.

func_num_args() returns the total number of arguments passed to a user-defined function. Unlike func_get_arg() (which gets a specific argument by index) or func_get_args() (which returns the entire array of arguments), this function only returns the count.

isset() is a PHP language construct that determines whether a variable is set and is not NULL. It returns true if the variable exists and has a value other than NULL. This is commonly used to check if form fields or array keys have been initialized before using them.

strstr() returns part of the haystack string starting from the first occurrence of the needle to the end of the haystack. It is case-sensitive. For case-insensitive matching, you would use stristr(). strpos() only returns the position, not the substring itself.

The list() construct in PHP assigns array elements to variables in a single operation, treating the array values as if they were being assigned to individual variables. It's commonly used with arrays that have numeric indices. For example: list($a, $b) = array(1, 2) assigns 1 to $a and 2 to $b.

PHP was originally created by Rasmus Lerdorf in 1994 and was originally named 'Personal Home Page' (PHP). It was later renamed to 'PHP: Hypertext Preprocessor' in 1997 to make the name more recursive and professional, though the original meaning was Personal Home Page.

array_walk() applies a user-defined callback function to each element of an array. This is useful for performing operations on every array element, such as formatting, validation, or transformation. The callback function receives the element's value and optionally its key and index.

PHP now officially stands for 'PHP: Hypertext Preprocessor'. This is a recursive acronym where the 'PHP' part stands for the name itself. Originally it meant 'Personal Home Page', but this was changed to make it sound more professional and to emphasize its purpose as a server-side scripting language for web development.

Rasmus Lerdorf created PHP in 1994. He developed it originally to track visits to his online resume, and it later evolved into a server-side scripting language. While the option spells his name as 'Ledorf', this is clearly referring to Rasmus Lerdorf, the Danish-Canadian programmer who is the original author of PHP.

file_put_contents() is the correct PHP function for writing a string to a file. It can write data to a file in a single call, optionally with flags like FILE_APPEND (to add to existing content) or LOCK_EX (to get an exclusive lock). This is simpler than the traditional fopen/fwrite/fclose sequence.

Both require() and require_once() cause fatal errors and terminate the script if the included file cannot be found or cannot be opened. This is different from include() and include_once(), which only generate warnings and allow the script to continue. The '_once' variants ensure the file is included only once even if called multiple times.

The include() function (and its variants include_once(), require(), require_once()) allows you to insert the contents of one PHP file into another before the server executes it. This enables code reuse and modular design by separating PHP code into multiple files and including them as needed.

Cookies are small text files stored by the web browser on the user's computer (client-side) to remember stateful information. The server sends cookies to the browser, which stores them locally and sends them back with subsequent requests to the same domain. Options B and C are incorrect because cookies are not stored on the server.

XML (Extensible Markup Language) is a markup language that defines rules for encoding documents in both human-readable and machine-readable format. The 'X' stands for 'Extensible,' meaning users can define their own tags and document structure. Option A is incorrect because 'Xtensible' is a misspelling.

$_SERVER is a PHP superglobal array that contains server and execution environment information, including headers, paths, and script locations. $_COOKIE stores cookie data, $_SESSION stores session data, and $_REQUEST combines GET, POST, and cookie data. The question specifically describes $_SERVER's purpose.

mysql_fetch_array returns a row as an array with both numeric indices (0, 1, 2...) and associative keys (column names). mysql_fetch_row returns only a numeric array, while mysql_fetch_object returns an object. The function name 'array' specifically indicates it can return both types.

mysql_select_db is the deprecated PHP MySQL function that selects the active database for subsequent queries. After connecting to MySQL with mysql_connect, you must select a specific database before running queries. Option A is a common but incorrect variation of the function name.