Zote include na require huleta (na kutekeleza) yaliyomo ya faili nyingine ya PHP ndani ya ya sasa. Tofauti pekee ni jinsi zinavyoshughulikia kushindwa: require husababisha fatal error ikiwa faili haipo, wakati include hutoa warning tu na kuendelea.
<?php
include "config.php"; // if missing → WARNING, script CONTINUES
require "database.php"; // if missing → FATAL ERROR, script STOPS
include → file missing → emits a Warning, execution continues (file's code skipped)
require → file missing → throws a Fatal Error, execution HALTS
Tumia require kwa faili ambazo application haiwezi kufanya kazi bila (core classes, critical config, database setup) — unataka isimame kabisa ikiwa hazipo. Tumia include kwa faili za hiari (mfano sidebar template) ambapo faili inayokosekana isivunje ukurasa.
require_once "functions.php"; // include the file ONLY if not already included
include_once "helper.php";
require_once/include_once huleta faili tu ikiwa haijaletwa tayari — muhimu kuepuka errors za "cannot redeclare function/class" wakati faili inaweza kuingizwa mara nyingi (mfano class definition iliyovutwa na faili kadhaa).
// included files share the SAME scope and can define functions, classes, variables
// config.php:
$dbHost = "localhost";
// main.php:
require "config.php";
echo $dbHost; // "localhost" — the variable is available
// ❌ old style — manually requiring every class file
require_once "User.php";
require_once "Order.php";
// ✅ modern — Composer AUTOLOADING loads classes on demand automatically
require "vendor/autoload.php"; // one line; classes load when used (PSR-4)
$user = new User(); // User.php loaded automatically
Katika PHP ya kisasa, mara chache hutumii manual require kwa classes — autoloader ya Composer huzipakia zinapohitajika. Bado hutumia require "vendor/autoload.php" mara moja kuiwasha (bootstrap).
Kuelewa include vs require ni ujuzi wa msingi lakini muhimu wa PHP — ndizo jinsi faili za PHP zinavyoshiriki code, na tofauti ina umuhimu kwa usahihi.
Jambo muhimu ni tabia ya kushindwa: require kwa faili muhimu (ili app ishindwe haraka na kwa uwazi ikiwa faili muhimu inakosekana) na include kwa za hiari (ili faili isiyo muhimu inayokosekana isivunje ukurasa).
Kujua variants za _once ni muhimu kivitendo kuzuia errors za kawaida za "cannot redeclare" kutoka kuingiza kwa bahati mbaya class au function definition mara mbili.
Muhimu sawasawa ni kuelewa muktadha wa kisasa: ingawa constructs hizi ni za msingi, PHP ya kisasa hutegemea Composer autoloading (kupakia classes zinapohitajika) badala ya kuhitaji kila faili kwa mkono, kwa hivyo katika code ya sasa mara nyingi hufanya tu require "vendor/autoload.php" mara moja na kuacha autoloading ishughulikie kilichobaki.
Kujua mechanics zote za include/require (na ni lini kila failure mode inafaa) na jinsi autoloading ya kisasa inavyochukua nafasi ya manual includes ni ujuzi wa kila siku kwa kufanya kazi na codebases za PHP za zamani na mpya.