Data types

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  1. Data Types in MediaWiki

This article provides a comprehensive introduction to data types in MediaWiki, geared towards beginners. Understanding data types is fundamental to effectively utilizing MediaWiki’s powerful features for content creation, templating, and extension development. We will cover the core data types, how they are handled, and how to leverage them for optimal results.

Introduction to Data Types

In the context of MediaWiki, "data types" refer to the kind of value a variable or a piece of data can hold. MediaWiki, built on PHP, inherits many of its data type characteristics. While MediaWiki primarily deals with text (strings) due to its nature as a wiki, understanding other data types allows for more complex functionality, especially when employing templates and extensions. Proper use of data types can significantly improve the reliability and efficiency of your wiki development. This is especially true when dealing with Variables and Functions.

Core Data Types

MediaWiki, and PHP underlying it, broadly categorizes data into the following types:

  • String: This is a sequence of characters, enclosed in single quotes (`'`) or double quotes (`"`). Strings represent text, and are the most commonly used data type in MediaWiki. For example, `'Hello, world!'` or `"This is a string."`. Double quotes allow for variable interpolation, meaning that variables within the string will be replaced with their values. Single quotes treat everything literally. The difference between single and double quotes is crucial when working with Templates.
  • Integer: Whole numbers without any decimal point. Examples include `10`, `-5`, `0`, `1000`. Integers are used for counting, indexing, and performing arithmetic operations. They are often used in Loops and conditional statements.
  • Float (Floating-point number): Numbers with a decimal point. Examples include `3.14`, `-2.5`, `0.0`. Floats are used to represent fractional values and are often used in calculations requiring precision. They are essential for financial data or scientific measurements.
  • Boolean: Represents truth values: `true` or `false`. Booleans are used in logical expressions and conditional statements to control the flow of execution. They are fundamental to Conditional Statements.
  • Array: An ordered collection of values. Arrays can contain values of different data types. Arrays are defined using the `array()` construct or shorthand notation in more recent PHP versions. They are incredibly versatile for storing and manipulating lists of data. Arrays are heavily used in Lists and tables.
  • Object: An instance of a class. Objects encapsulate data (properties) and code (methods) that operate on that data. Objects are essential for object-oriented programming and are widely used in MediaWiki extensions. Understanding Classes is key to working with objects.
  • NULL: Represents the absence of a value. It's often used to indicate that a variable has not been assigned a value or that a function has not returned a value. Checking for `NULL` is important to prevent errors.
  • Resource: A reference to an external resource, such as a file handle or a database connection. Resources are managed by PHP and are typically used by extensions interacting with external systems.

String Manipulation

Strings are arguably the most important data type in MediaWiki. MediaWiki's content is fundamentally stored as strings. PHP provides a rich set of functions for manipulating strings. Here are some common operations:

  • Concatenation: Joining two or more strings together using the `.` operator. For example, `'Hello' . ' ' . 'world!'` results in `'Hello world!'`.
  • Length: Determining the number of characters in a string using the `strlen()` function.
  • Substring: Extracting a portion of a string using the `substr()` function.
  • Replacement: Replacing occurrences of a substring within a string using the `str_replace()` function.
  • Case Conversion: Converting a string to uppercase using `strtoupper()` or lowercase using `strtolower()`.
  • Trimming: Removing whitespace from the beginning and end of a string using `trim()`.
  • Searching: Finding the position of a substring within a string using `strpos()`.

These functions are frequently used within Templates to process and format text.

Numeric Data Types (Integer & Float)

While MediaWiki primarily deals with strings, numeric data types are crucial for calculations and comparisons.

  • Arithmetic Operators: PHP supports standard arithmetic operators: `+` (addition), `-` (subtraction), `*` (multiplication), `/` (division), `%` (modulo – remainder after division).
  • Type Conversion: PHP automatically converts data types in certain situations. For example, if you add a string containing a number to an integer, PHP will attempt to convert the string to an integer before performing the addition. Explicit type conversion can be achieved using functions like `intval()` (convert to integer) and `floatval()` (convert to float). Understanding Type Casting is important for avoiding unexpected behavior.
  • Comparison Operators: Used to compare numeric values: `==` (equal to), `!=` (not equal to), `>` (greater than), `<` (less than), `>=` (greater than or equal to), `<=` (less than or equal to).

Boolean Logic

Booleans are used for making decisions in your wiki code.

  • Logical Operators: PHP provides logical operators: `&&` (logical AND), `||` (logical OR), `!` (logical NOT). These operators are used to combine or negate boolean expressions.
  • Truthiness: In PHP, values other than `false`, `0`, `""` (empty string), `NULL`, and `array()` are considered "truthy" – they evaluate to `true` in a boolean context. This can sometimes lead to unexpected behavior, so it's important to be aware of it. This concept is tied to Truth Tables.

Arrays: Working with Collections

Arrays are powerful for storing and managing collections of data.

  • Indexed Arrays: Arrays with numeric keys, starting from 0. For example, `$myArray = array('apple', 'banana', 'cherry');`.
  • Associative Arrays: Arrays with string keys, allowing you to associate values with meaningful names. For example, `$myArray = array('name' => 'John', 'age' => 30);`.
  • Multidimensional Arrays: Arrays containing other arrays, allowing you to create complex data structures.
  • Array Functions: PHP provides numerous functions for working with arrays: `count()` (get the number of elements), `sort()` (sort the array), `array_push()` (add an element to the end), `array_pop()` (remove the last element), etc.

Arrays are extensively used in Database Interactions and Data Structures.

Objects and Classes

Objects are instances of classes. Classes define the blueprint for creating objects, specifying their properties (data) and methods (functions).

  • Class Definition: Classes are defined using the `class` keyword.
  • Object Creation: Objects are created using the `new` keyword.
  • Properties: Variables within a class that hold data.
  • Methods: Functions within a class that operate on the object's data.
  • Object-Oriented Programming (OOP): A programming paradigm based on objects and classes. OOP principles like encapsulation, inheritance, and polymorphism can significantly improve code organization and maintainability.

Objects are primarily used in Extension Development within MediaWiki.

NULL Values

The `NULL` value represents the absence of a value. It is important to check for `NULL` before attempting to use a variable that might not have been assigned a value.

  • `isset()` Function: Checks if a variable is set and is not `NULL`.
  • `empty()` Function: Checks if a variable is empty (e.g., `""`, `0`, `NULL`, `false`, `array()`).
  • `is_null()` Function: Checks if a variable is exactly `NULL`.

Handling `NULL` values correctly prevents errors and ensures the stability of your wiki applications.

Data Type Detection

PHP provides functions to determine the data type of a variable:

  • `gettype()`: Returns a string representing the data type of the variable.
  • `is_string()`, `is_int()`, `is_float()`, `is_bool()`, `is_array()`, `is_object()`, `is_null()`: These functions return `true` if the variable is of the specified type, and `false` otherwise.

Knowing the data type of a variable allows you to perform appropriate operations and avoid errors.

Data Types and MediaWiki Templating

Data types play a crucial role in MediaWiki templating. When passing data to templates, it's important to understand how different data types are handled. Strings are automatically converted to strings, numbers are converted to strings, and arrays are often iterated over. Careful consideration of data types is essential for creating robust and reliable templates. See Template Development for more details.

Advanced Concepts & Related Topics

  • Type Hinting (PHP 7+): Specifying the expected data type of function parameters and return values.
  • Strict Typing (PHP 7+): Enforcing type checking more rigorously.
  • Serialization: Converting data structures (e.g., arrays, objects) into a string representation for storage or transmission. Useful for caching.
  • JSON (JavaScript Object Notation): A lightweight data-interchange format that is often used with web APIs.
  • XML (Extensible Markup Language): Another data-interchange format commonly used in web applications.
  • Regular Expressions: Powerful patterns for matching and manipulating strings. Useful for Data Validation.
  • SQL Data Types: Understanding the data types used in your database (e.g., `VARCHAR`, `INT`, `FLOAT`, `DATE`) is essential for efficient database interactions. See Database Queries.
  • Caching Strategies: Understanding the data types you are caching is crucial for efficient caching.
  • Performance Optimization: Using the correct data types can impact the performance of your wiki.
  • Security Considerations: Improper handling of data types can lead to security vulnerabilities. Always sanitize user input and validate data types.
  • Technical Analysis: Understanding data types is crucial for handling financial data in technical analysis. See Candlestick Patterns, Moving Averages, and Bollinger Bands.
  • Market Trends: Analyzing data types related to market data is essential for identifying trends. See Trend Following, Support and Resistance, and Fibonacci Retracements.
  • Trading Signals: Accurate data type handling is vital for generating reliable trading signals. See MACD, RSI, and Stochastic Oscillator.
  • Risk Management: Correctly handling numerical data types is crucial for risk assessment.
  • Portfolio Diversification: Understanding data types associated with different assets.
  • Algorithmic Trading: Requires precise data type handling for automated trading strategies.
  • Backtesting: Data types must be accurate for reliable backtesting results.
  • Volatility Analysis: Correctly handling numerical data types is essential for volatility analysis.
  • Correlation Analysis: Analyzing relationships between data types.
  • Elliott Wave Theory: Requires accurate data type interpretation for wave patterns.
  • Chart Patterns: Identifying patterns requires accurate data visualization.
  • Gap Analysis: Identifying gaps in data requires accurate data type handling.
  • Volume Analysis: Analyzing trading volume requires accurate data type interpretation.
  • Price Action Trading: Analyzing price movements requires accurate data visualization.
  • Day Trading: Requires rapid and accurate data type handling.
  • Swing Trading: Requires accurate data type interpretation for swing patterns.
  • Long-Term Investing: Requires long-term data storage and accurate data type handling.
  • Fundamental Analysis: Requires accurate data type interpretation for financial statements.
  • Value Investing: Requires accurate data type interpretation for asset valuation.


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