PHP Access Modifiers: Public, Protected, Private & Encapsulation

In professional software design, permitting outside scripts to freely alter the internal variables of an object leads to catastrophic bugs, security vulnerabilities, and data corruption. Encapsulation is the fundamental OOP principle of restricting direct access to an object's internal components. In PHP, this control is enforced through Visibility Access Modifiers: public, protected, and private.

The Visibility Rulebook: Public vs Protected vs Private

Encapsulation in Action: Getters and Setters

By declaring properties private and providing public getter and setter methods, you can enforce strict business validation rules:

<?php
    class StudentRecord {
        private string $name;
        private float $gpa; // Protected from unauthorized direct tampering

        public function __construct(string $name, float $initialGpa) {
            $this->name = $name;
            $this->setGpa($initialGpa); // Validate via setter
        }

        // Getter for GPA (Read-Only access)
        public function getGpa(): float {
            return $this->gpa;
        }

        // Setter for GPA (Enforces validation)
        public function setGpa(float $newGpa): void {
            if ($newGpa < 0.0 || $newGpa > 4.0) {
                throw new InvalidArgumentException("GPA must be between 0.0 and 4.0.");
            }
            $this->gpa = $newGpa;
        }
    }

    $student = new StudentRecord("Deepa", 3.8);
    echo "Current GPA: " . $student->getGpa() . "<br>";

    // Valid update:
    $student->setGpa(3.95);
    echo "Updated GPA: " . $student->getGpa() . "<br>";

    // Invalid attempt: Direct access triggers Fatal Error
    // $student->gpa = 5.0; // Fatal Error: Cannot access private property
?>

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