Script PHP and Databases 2026 Comprehensive Review

Vocabulary and concept flashcards covering PHP basics, relational databases, SQL, WordPress development, web security, and transaction management as presented in the lecture notes.

PHP (Hypertext Preprocessor)

A server-side scripting language used to develop dynamic websites and web applications where code is executed on the server and the browser receives only the generated result (usually HTML).

Case-sensitivity in PHP

Variables are case-sensitive; for example, $name and $Name are treated as two different variables.

Global Scope

The visibility range of variables defined outside of functions; they cannot be accessed directly inside a function without specific keywords.

Local Scope

The visibility range of variables defined inside a function; they exist only within that specific function.

Scalar Data Types

The basic data types in PHP consisting of Boolean (true/false), Integer (whole numbers), Float (decimal numbers), and String (text).

NULL

A special data type representing a variable that has no value.

Point Operator (.)

The operator used in PHP to connect (concatenate) multiple strings together.

Explicit Type Casting

The manual conversion of a variable's data type, such as using (int), (float), (string), or (bool) before a value.

var_dump()

A function used to output the content of a variable along with its data type information.

Identity Operator (===)

A comparison operator that checks if two values are equal and of the same data type.

Include_once

A function used to include a file into a script, ensuring it is only embedded one time to prevent duplicate code errors.

php.ini

The central configuration file for PHP that the interpreter reads before executing a program to determine behavior and settings.

Associative Array

An array in PHP where strings are used as keys specifically mapped to values instead of automatic integer indexing.

isset()

A function used to check if a variable or an array key is set and is not NULL.

Superglobals

Predefined variables that are always available in all scopes, such as $_GET, $_POST, $_SERVER, and $_SESSION.

implode()

A PHP function that joins the elements of an array into a single string using a specified glue character.

explode()

A PHP function that splits a single string into an array based on a specified delimiter.

htmlspecialchars()

A critical security function that converts HTML special characters into HTML entities, preventing HTML code injection and XSS attacks.

strpos()

A function that searches for the position of a specific text within a string, returning false if the text is not found.

GET Method

A data transmission method where data is visibly appended to the URL, suitable for bookmarks and non-sensitive search queries.

POST Method

A data transmission method where data is sent within the HTTP body, suitable for large amounts of data and sensitive form inputs.

Null-Coalescing Operator (??)

An operator used to return the first operand if it exists and is not NULL; otherwise, it returns the second operand.

DBMS (Database Management System)

Software used to manage, store, change, delete, and search data within a database (e.g., MariaDB, MySQL, Oracle).

Redundancy

The undesirable condition where the same information is stored multiple times in a database, leading to wasted storage and potential inconsistencies.

Information System (IS)

A system consisting of Users, Applications, the DBMS, and the Database used to collect, store, and process information.

External Level (Three-Level Architecture)

The user's view of the database, showing only the specific data they are authorized and required to see.

Conceptual Level (Three-Level Architecture)

The level describing the entire database structure, including tables, relationships, and rules.

Relation

In database terminology, this refers to the content (set of rows) of a table.

Tuple

The relational database term for a single row in a table.

Primary Key

An attribute or set of attributes that uniquely and minimally identifies every tuple in a relation, containing no NULL values.

Referential Integrity

An integrity rule stating that every foreign key must point to an existing primary key to prevent orphaned records.

Selection ($\sigma$)

A relational algebra operation that selects specific rows from a table based on a condition.

Projection ($\pi$)

A relational algebra operation that selects specific columns (attributes) from a table.

Inner Join

A join operation that returns only the records where there is a match in both tables.

DQL (Data Query Language)

The part of SQL used to query data, primarily using the SELECT command.

DML (Data Manipulation Language)

The part of SQL used to change data using commands like INSERT, UPDATE, and DELETE.

DDL (Data Definition Language)

The part of SQL used to define database structures using commands like CREATE, ALTER, and DROP.

GROUP BY

A SQL clause used to group rows that have the same values into summary rows, often used with aggregate functions (COUNT, SUM, AVG).

HAVING

A SQL clause used specifically to filter groups after a GROUP BY operation, whereas WHERE filters individual records before grouping.

Entity (ER-Model)

A uniquely identifiable object in the real world (e.g., a specific person or car) represented as a record in a database.

Content Management System (CMS)

A web platform that separates content (stored in a database) from presentation (themes/templates), allowing collaborative content creation.

Frontcontroller Pattern

A design pattern where all requests to a website are processed centrally through a single point (e.g., index.php).

WordPress Hooks (Action Hooks)

Mechanism used to insert custom PHP code into specific entry points of the WordPress execution flow using add_action().

Confidentiality (Security Goal)

The protection goal ensuring that sensitive information is only accessible by authorized persons.

Integrity (Security Goal)

The protection goal ensuring that data remains correct and has not been manipulated by unauthorized parties.

Availability (Security Goal)

The protection goal ensuring that applications and data are reachable/usable whenever needed.

Transaction

A sequence of database operations treated as a single unit that moves a database from one consistent state to another.

ACID (Atomicity)

The principle that a transaction is all-or-nothing; it is either fully completed or completely rolled back.

Dirty Read

A synchronization problem where a transaction reads data that was modified by another transaction but has not yet been committed.

Lost Update

A conflict occurring when two transactions read the same value and then overwrite each other's changes.

View

A virtual table based on a stored SQL query that does not store data itself but displays data from underlying tables.

Normalization

The process of optimizing a database model to eliminate redundancies and prevent anomalies (1NF, 2NF, 3NF).

Functional Dependency ($X \rightarrow Y$)

A relationship where the value of attribute X uniquely determines the value of attribute Y.

Session (PHP)

A method to store user data across multiple page visits by storing data on the server and a unique ID (Cookie) on the client.

Hashing

The process of transforming a password into a unique string of characters for secure storage, which cannot be easily reversed.

Serializability

A property of a schedule of transactions where the interleaved execution results in the same effect as a serial execution.

Conflict Graph

A directed graph used to test serializability; if it contains a cycle, the schedule is not serializable.