What are the differences in behavior between isset() function and comparison operators when dealing with instance variables in PHP?

When dealing with instance variables in PHP, the isset() function is used to check if a variable is set and not null, while comparison operators like == or === are used to compare values. isset() is specifically used to check if a variable exists, while comparison operators are used to compare values for equality or identity. 

// Using isset() to check if an instance variable is set
class MyClass {
    public $myVar;
}

$obj = new MyClass();
if (isset($obj->myVar)) {
    echo 'myVar is set';
} else {
    echo 'myVar is not set';
}

// Using comparison operators to compare instance variable values
class MyClass {
    public $myVar = 'Hello';

    public function compareVar($value) {
        if ($this->myVar == $value) {
            echo 'Values match';
        } else {
            echo 'Values do not match';
        }
    }
}

$obj = new MyClass();
$obj->compareVar('Hello');

Keywords

isset comparison operators instance variables behavior PHP

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