? PHP OOP Conditional Functions

? Quick Overview

PHP allows functions to be declared conditionally using control structures like if and else. When combined with Object-Oriented Programming, this technique helps define helper logic only when required.

? Key Concepts

Conditional function declarations
Runtime evaluation of functions
Using function_exists() safely
Combining global functions with OOP classes

? Syntax & Theory

In PHP, conditional functions are evaluated at runtime. Once declared, they cannot be redeclared later. This makes them useful for environment checks, polyfills, and compatibility layers inside OOP-based projects.

? Code Example

? View Code Example

// Class with a regular OOP method
<?php
class Logger {
    public function log($msg) {
        echo "Default Logger: $msg<br>";
    }
}

// Conditional function declaration using function_exists
if (!function_exists("customLogger")) {
    function customLogger($msg) {
        echo "Custom Logger Function: $msg<br>";
    }
}

// Calling both OOP method and conditional function
$log = new Logger();
$log->log("OOP Method Called");
customLogger("Conditional Function Called");
?>

? Live Output / Explanation

The Logger class executes its method normally. The customLogger() function is only declared once, preventing redeclaration errors and allowing safe conditional execution.

? Interactive Concept

Think of conditional functions as feature switches. They activate specific logic only when conditions are met, improving flexibility and compatibility across PHP versions and environments.

? Use Cases

PHP version-based polyfills
Environment-specific helpers
Optional logging or debugging utilities
Plugin or module-based architectures

✅ Tips & Best Practices

Always wrap conditional functions with function_exists()
Keep conditional logic minimal and clear
Prefer class methods when behavior belongs to an object
Use conditional functions mainly for compatibility layers

? Try It Yourself

Create a Calculator class with a conditional helper function
Define a version-based polyfill using PHP_VERSION
Switch logging behavior based on environment flags
Test redeclaration behavior by removing function_exists()