Home Backend Development PHP Tutorial How to Avoid Global Variables When Accessing a Database Object within a Class?

How to Avoid Global Variables When Accessing a Database Object within a Class?

Dec 22, 2024 pm 03:00 PM

How to Avoid Global Variables When Accessing a Database Object within a Class?

Using Global Variables within a Class

Creating pagination functionality involves accessing a database object from within a class. However, attempting to access an outside variable inside the class can lead to errors. Let's delve into possible solutions to handle this issue.

To address the fatal error "Call to a member function query() on a non-object," the database object needs to be accessible within the class. Instead of using global variables, a more appropriate approach is to inject the database object into the class or its methods.

Dependency Injection

One method is to inject the database object into the class constructor, as shown below:

include_once("pagi.php");

$db = new DB_MySQL("localhost", "root", "", "test"); // connect to the database

$pagination = new Paginator($db);
$records = $pagination->get_records("SELECT * FROM `table`");

class Paginator
{    
    protected $db;

    public function __construct(DB_MySQL $db)
    {
        $this->db = $db;
    }

    public function get_records($q) {
        $x = $this->db->query($q);
        return $this->db->fetch($x);
    }
}

This allows the pagination class to access the database object directly.

Method Injection

Another option is to inject the database object into the specific method that requires it:

$pagination = new Paginator();
$records = $pagination->get_records("SELECT * FROM `table`", $db);

class Paginator
{
    public function get_records($q, DB_MySQL $db) {
        $x = $db->query($q);
        return $db->fetch($x);
    }
}

This provides more flexibility when multiple methods have varying database requirements.

Benefits of Dependency Injection

Compared to using global variables, dependency injection offers several advantages:

  • Explicitly Defined Dependencies: It makes it clear which objects depend on others, eliminating hidden dependencies.
  • Loose Coupling: The class can easily switch to a different or mocked database object for testing purposes.
  • Testability: Unit tests can focus solely on the class without interfering with database functionality.
  • Extensibility: It allows the use of multiple databases or other frameworks without major code changes.

The above is the detailed content of How to Avoid Global Variables When Accessing a Database Object within a Class?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

PHP Tutorial
1596
276
Object-Relational Mapping (ORM) Performance Tuning in PHP Object-Relational Mapping (ORM) Performance Tuning in PHP Jul 29, 2025 am 05:00 AM

Avoid N 1 query problems, reduce the number of database queries by loading associated data in advance; 2. Select only the required fields to avoid loading complete entities to save memory and bandwidth; 3. Use cache strategies reasonably, such as Doctrine's secondary cache or Redis cache high-frequency query results; 4. Optimize the entity life cycle and call clear() regularly to free up memory to prevent memory overflow; 5. Ensure that the database index exists and analyze the generated SQL statements to avoid inefficient queries; 6. Disable automatic change tracking in scenarios where changes are not required, and use arrays or lightweight modes to improve performance. Correct use of ORM requires combining SQL monitoring, caching, batch processing and appropriate optimization to ensure application performance while maintaining development efficiency.

Building Immutable Objects in PHP with Readonly Properties Building Immutable Objects in PHP with Readonly Properties Jul 30, 2025 am 05:40 AM

ReadonlypropertiesinPHP8.2canonlybeassignedonceintheconstructororatdeclarationandcannotbemodifiedafterward,enforcingimmutabilityatthelanguagelevel.2.Toachievedeepimmutability,wrapmutabletypeslikearraysinArrayObjectorusecustomimmutablecollectionssucha

Handling Cryptocurrency Calculations: Why BCMath is Essential in PHP Handling Cryptocurrency Calculations: Why BCMath is Essential in PHP Aug 01, 2025 am 07:48 AM

BCMathisessentialforaccuratecryptocurrencycalculationsinPHPbecausefloating-pointarithmeticintroducesunacceptableroundingerrors.1.Floating-pointnumberslike0.1 0.2yieldimpreciseresults(e.g.,0.30000000000000004),whichisproblematicincryptowhereprecisionu

Strings as Value Objects: A Modern Approach to Domain-Specific String Types Strings as Value Objects: A Modern Approach to Domain-Specific String Types Aug 01, 2025 am 07:48 AM

Rawstringsindomain-drivenapplicationsshouldbereplacedwithvalueobjectstopreventbugsandimprovetypesafety;1.Usingrawstringsleadstoprimitiveobsession,whereinterchangeablestringtypescancausesubtlebugslikeargumentswapping;2.ValueobjectssuchasEmailAddressen

Understanding Constant Expression Evaluation in PHP's Engine Understanding Constant Expression Evaluation in PHP's Engine Jul 29, 2025 am 05:02 AM

PHPevaluatesconstantexpressionsatcompiletimetoimproveperformanceandenableearlyerrordetection.1.Constantexpressionevaluationmeanscomputingvaluesduringcompilationwhenalloperandsareknownconstantslikeliterals,classconstants,orpredefinedconstants.2.PHP’se

Using PHP for Data Scraping and Web Automation Using PHP for Data Scraping and Web Automation Aug 01, 2025 am 07:45 AM

UseGuzzleforrobustHTTPrequestswithheadersandtimeouts.2.ParseHTMLefficientlywithSymfonyDomCrawlerusingCSSselectors.3.HandleJavaScript-heavysitesbyintegratingPuppeteerviaPHPexec()torenderpages.4.Respectrobots.txt,adddelays,rotateuseragents,anduseproxie

Navigating the Pitfalls of Floating-Point Inaccuracy in PHP Navigating the Pitfalls of Floating-Point Inaccuracy in PHP Jul 29, 2025 am 05:01 AM

Floating point numbers are inaccurate is a common problem in PHP. The answer is that it uses IEEE754 double-precision format, which makes decimal decimals unable to be accurately represented; numbers such as 1.0.1 or 0.2 are infinite loop decimals in binary, and the computer needs to truncate them to cause errors; 2. When comparing floating point numbers, you should use tolerance instead of ==, such as abs($a-$b)

Unpacking Performance: The Truth About PHP Switch vs. if-else Unpacking Performance: The Truth About PHP Switch vs. if-else Aug 02, 2025 pm 04:34 PM

Switchcanbeslightlyfasterthanif-elsewhencomparingasinglevariableagainstmultiplescalarvalues,especiallywithmanycasesorcontiguousintegersduetopossiblejumptableoptimization;2.If-elseisevaluatedsequentiallyandbettersuitedforcomplexconditionsinvolvingdiff

See all articles