How do you verify the existence of a property in PHP objects and classes?

Property Existence Verification in PHP Objects and Classes

PHP does not natively support a pure object variable check. This question explores methods to determine if a property exists within a PHP object or class.

Property_exists() Function

The property_exists() function accepts two parameters: the class name or object instance and the property name to check. If the property exists in the specified target, the function returns true, otherwise false.

Example:

<code class="php">$ob = (object) array('a' => 1, 'b' => 12); 

if (property_exists($ob, 'a')) {
    echo "Property 'a' exists in the object.";
}</code>

Isset() Function

The isset() function can also be used to check property existence. However, note that it will return false if the property is explicitly set to null.

Example:

<code class="php">$ob->a = null;
if (isset($ob->a)) {
    echo "Property 'a' exists in the object, but is set to null.";
} else {
    echo "Property 'a' does not exist in the object.";
}</code>

Difference between property_exists() and isset()

property_exists() checks for the existence of a declared property, regardless of its value. isset() checks for both property existence and whether the value is not null.

Example Demonstrating the Difference:

<code class="php">class Foo {
   public $bar = null;
}

$foo = new Foo();

var_dump(property_exists($foo, 'bar')); // true
var_dump(isset($foo->bar)); // false</code>

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