Tag: php-internals
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Memory-Mapped Files
A file mapped directly into a process's virtual address space — reads and writes go through the OS page cache rather than read()/write() syscalls, enabling fast access to large files and shared memory between processes.
2mo ago
linux advanced
Copy-on-Write (CoW) in PHP Arrays PHP 7.0+
PHP arrays are not copied when assigned or passed to functions — they share the same internal buffer until one copy is modified. Only then does PHP perform a real copy. This makes reading large arrays cheap but silent mutations expensive.
2mo ago
php intermediate
OPcache Internals — How Bytecode Caching Works PHP 5.5+
OPcache compiles PHP source files to bytecode once and stores the result in shared memory — subsequent requests skip parsing and compilation entirely, making PHP 5–10x faster for I/O-bound workloads.
2mo ago
php intermediate
PHP Execution Model — Shared-Nothing Architecture PHP 5.0+
Each PHP request runs in a completely isolated process or thread — no memory, globals, or state is shared between requests. Every request bootstraps the entire application from scratch and discards everything when it ends.
2mo ago
php intermediate
PHP Garbage Collection Internals (Cycle Collector) PHP 5.3+
PHP uses reference counting as its primary memory management strategy — when a value's reference count drops to zero it is freed immediately. A secondary cycle collector handles circular references that reference counting alone cannot free.
2mo ago
php advanced
PHP Memory Model — Zval & Copy-on-Write PHP 7.0+
PHP stores every value in a zval (Zend value) container that holds the type, value, and a reference count. Arrays and strings are copied lazily — the copy only happens when one copy is modified (copy-on-write), making passing large values cheap until mutation.
2mo ago
php advanced
Zend Engine Versions — 1 Through 4
The Zend Engine is the virtual machine that compiles and executes PHP code. Version 1 (PHP 3) introduced the modern parser; v2 (PHP 5) added OOP; v3 (PHP 7) doubled performance; v4 (PHP 8) added JIT compilation.
2mo ago
php intermediate