PHP terms
The engine behind the web's most-used server-side language
PHP powers an enormous portion of the web — from WordPress and Laravel to custom e-commerce platforms. This category covers the language internals, core functions, OOP features, type system, performance patterns, and PHP-specific quirks that every serious PHP developer should understand deeply. Whether you are writing procedural scripts or building full-stack applications with modern PHP 8.x features, these terms form the foundation.
More on PHP
History
PHP began in 1995 as a simple set of Perl scripts created by Rasmus Lerdorf to track visits to his personal website, evolving into a dedicated language called "Personal Home Page Tools." By version 3.0 (1997–1998), it became a fully-featured server-side scripting language adopted widely for web development, with PHP 4 (2000) introducing the Zend Engine and significantly improving performance and architecture. The object-oriented paradigm matured substantially in PHP 5 (2004), bringing proper class-based inheritance, interfaces, and exception handling, while PHP 7 (2015) delivered major performance gains and type declarations. Modern PHP (8.0+, released 2020 onwards) introduced named arguments, attributes, union types, match expressions, and later DNF types and fibers, reflecting maturation toward enterprise-grade systems while maintaining backward compatibility and its historical accessibility for rapid web development. Today, PHP powers over 75% of websites with known server-side technology, ranging from simple content management systems to complex frameworks like Laravel and Symfony.
Key concepts
- Constants (define vs const)
- Variables & Type Basics
- Arrays & Array Functions
- Functions & Closures
- Object-Oriented Programming Basics
- Exception Handling (try/catch/finally)
- Error Handling in PHP
- Composer & Dependency Management
Best references
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PHP Official Documentation The canonical reference for all PHP language features, functions, and standard library. Essential for accurate syntax, behavior, and version-specific changes across all 270 terms in this category.
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PHP RFC Archive Official Request for Comments documenting the design and rationale behind language features like attributes, enums, fibers, and type system enhancements. Invaluable for understanding why features were introduced and their historical context.
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Modern PHP by Josh Lockhart Seminal practical guide covering contemporary PHP patterns, best practices, and ecosystem tools like Composer. Bridges language features with real-world architectural patterns relevant to dependency injection and error handling.
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PHP-FIG Standards (PSR) Framework Interoperability Group specifications defining community standards for autoloading (PSR-4), coding style, interfaces, and more. Critical for understanding conventions around autoloaders, DI containers, and class organization.
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Composer Official Documentation Complete reference for dependency management, autoloading configuration, and composer scripts. Essential for understanding the modern PHP ecosystem and how Composer resolves the terms related to package management and autoloading.
✦ Latest in PHP
Typed relationships here
Edges touching a PHP term.
- Regex in Loop Leverages preg_match() / preg_replace() 5h
- HTTP Cookies in PHP Enables Cross-Site Request Forgery (CSRF) 15h
- password_hash() Leverages Argon2 Password Hashing 18h
- Dependency Injection Applies Dependency Inversion Principle (DIP) 18h
- SameSite Cookie Attribute Configures HTTP Cookies in PHP 1d
A value object requires immutability — its whole equality-by-value contract depends on state never changing after construction. PHP's readonly classes are a language-level mechanism that applies exactly that immutability by making every declared property readonly, so the value object's defining guarantee is enforced by the compiler rather than by convention. Immutability is the shared property that carries the conceptual requirement from value_object down to the concrete PHP feature that implements it.
PHP's readonly classes connect to the problem of side effects by means of immutability: marking a class readonly enforces that its properties can't be mutated after construction, which is exactly the property immutability uses to mitigate side effects like argument mutation and shared-state changes. The readonly mechanism is the concrete language feature that realizes immutability, and immutability in turn is what carries the predictability guarantee back to the side-effects concern. Without immutability as the bridge, readonly_classes is just a PHP syntax detail with no inherent reason to relate to the general quality problem of side effects.
Type safety relates to type coercion mainly by means of strict_types: flipping on strict_types=1 is the concrete switch that turns PHP's silent scalar conversions into hard TypeErrors. So the quality goal of type safety actually attacks the coercion problem through this declaration — strict_types is what carries the enforcement from the abstract goal down to suppressing the specific runtime behavior, and without it the coercion keeps happening even with typed signatures present.
each() & list() — Deprecated Iteration
PHP 3.0+
each() was deprecated in PHP 7.2 and removed in PHP 8 — replace while(list($k,$v)=each($arr)) with foreach. list() itself is still valid as [] destructuring.
3mo ago
PHP beginner
Engine Exceptions — Error Hierarchy (PHP 7.0)
PHP 7.0+
PHP 7.0 made fatal engine errors catchable as Error subclasses — TypeError, ParseError, ArithmeticError, DivisionByZeroError — via the shared Throwable interface.
3mo ago
PHP intermediate
Enums — First-Class Enumerations (PHP 8.1)
PHP 8.1+
PHP 8.1 native enums replace class constant hacks — providing type-safe, enumerable, matchable values with optional backing values (: string or : int).
3mo ago
PHP intermediate
ereg() / eregi() — POSIX Regex Removed in PHP 7
PHP 3.0+
ereg() and eregi() were POSIX regex functions removed in PHP 7.0 — replace with preg_match() (PCRE) which is faster, more powerful, and the standard since PHP 4.
3mo ago
PHP beginner
Error Logging
PHP 4.0+
2
Recording application errors, exceptions, and diagnostic information to persistent storage — essential for diagnosing production issues where display_errors must be off and errors are invisible to users.
3mo ago
PHP beginner
Error Reporting & Display
PHP 4.0+
1
PHP's error_reporting level and display_errors directive control which errors are shown and where — development needs E_ALL with display on; production needs E_ALL with display off and logging on.
3mo ago
PHP beginner
Exception Handling Introduced (PHP 5)
PHP 5.0+
PHP 5 introduced try/catch/finally and the Exception class — replacing PHP 4's procedural error handling with structured exception-based patterns.
3mo ago
PHP beginner
Enum::cases() & Enum from()/tryFrom()
PHP 8.1+
Backed enums provide from() (throws on miss) and tryFrom() (returns null) for value lookup, plus cases() to get all cases — essential for forms and validation.
3mo ago
PHP intermediate
Enums Implementing Interfaces
PHP 8.1+
PHP 8.1 enums can implement interfaces, allowing them to be used wherever an interface is expected — enabling polymorphic enum-based dispatch.
3mo ago
PHP intermediate
Exception Hierarchy (Throwable, Error, Exception)
PHP 7.0+
1
PHP 7+ unified exceptions and fatal errors under the Throwable interface — catch Throwable to handle both Error and Exception in one block.
3mo ago
PHP intermediate
Enum Methods, Interfaces & Constants (PHP 8.1)
PHP 8.1+
PHP 8.1 enums support methods, interface implementation, constants, and static factory methods — making them full-featured types, not just value lists.
3mo ago
PHP intermediate
Enums (PHP 8.1)
PHP 8.1+
3
Native enumerations providing type-safe named constants that replace class-constant patterns and stringly-typed values.
3mo ago
PHP intermediate
Error Handling in PHP
PHP 5.0+
2
Uncaught errors and verbose error output expose stack traces, file paths, and credentials to attackers.
CWE-209 OWASP A9:2021
3mo ago
PHP beginner
5.3
escapeshellarg()
PHP 5.0+
1
Wraps a string in single quotes and escapes internal quotes for safe use as a single shell argument.
3mo ago
PHP intermediate
Exception Hierarchy & Custom Exceptions
PHP 5.0+
Defining domain-specific exception classes that extend SPL exceptions provides semantic meaning and enables granular catch blocks.
3mo ago
PHP intermediate
extract() — Dangerous Variable Injection
PHP 4.0+
1
extract() creates local variables from an array, allowing attackers to overwrite existing variables if input is unsanitised.
CWE-621 OWASP A3:2021
3mo ago
PHP beginner
9.8
Exception Handling (try/catch/finally)
PHP 5.0+
3
PHP's structured error handling mechanism that separates error-path code from the happy path and ensures resource cleanup.
3mo ago
PHP intermediate