PHP check whether property exists in object or class

Question

I understand PHP does not have a pure object variable, but I want to check whether a property is in the given object or class.

$ob = (object) array('a' => 1, 'b' => 12); 

or

$ob = new stdClass;
$ob->a = 1;
$ob->b = 2;

In JS, I can write this to check if variable a exists in an object:

if ('a' in ob)

In PHP, can anything like this be done?

Answer 1

property_exists( mixed $class , string $property )

if (property_exists($ob, 'a')) 

isset( mixed $var [, mixed $... ] )

if (isset($ob->a))

isset() will return false if property is null

Example 1:

$ob->a = null
var_dump(isset($ob->a)); // false

Example 2:

class Foo
{
   public $bar = null;
}

$foo = new Foo();

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

Answer 2

To check if the property exists and if it's null too, you can use the function property_exists().

Docs: http://php.net/manual/en/function.property-exists.php

As opposed with isset(), property_exists() returns TRUE even if the property has the value NULL.

bool property_exists ( mixed $class , string $property )

Example:

if (property_exists($testObject, $property)) {
    //do something
}

Answer 3

Neither isset or property_exists work for me.

• isset returns false if the property exists but is NULL.
• property_exists returns true if the property is part of the object's class definition, even if it has been unset.

I ended up going with:

    $exists = array_key_exists($property, get_object_vars($obj));

Example:

    class Foo {
        public $bar;

        function __construct() {
            $property = 'bar';

            isset($this->$property); // FALSE
            property_exists($this, $property); // TRUE
            array_key_exists($property, get_object_vars($this)); // TRUE

            unset($this->$property);

            isset($this->$property); // FALSE
            property_exists($this, $property); // TRUE
            array_key_exists($property, get_object_vars($this)); // FALSE

            $this->$property = 'baz';

            isset($this->$property); // TRUE
            property_exists($this, $property); // TRUE
            array_key_exists($property, get_object_vars($this));  // TRUE
        }
    }

Answer 4

Solution

echo $person->middleName ?? 'Person does not have a middle name';

To show how this would look in an if statement for more clarity on how this is working.

if($person->middleName ?? false) {
    echo $person->middleName;
} else {
    echo 'Person does not have a middle name';
}

Explanation

The traditional PHP way to check for something's existence is to do:

if(isset($person->middleName)) {
    echo $person->middleName;
} else {
    echo 'Person does not have a middle name';
}

OR for a more class specific way:

if(property_exists($person, 'middleName')) {
    echo $person->middleName;
} else {
    echo 'Person does not have a middle name';
}

These are both fine in long form statements but in ternary statements they become unnecessarily cumbersome like so:

isset($person->middleName) ? echo $person->middleName : echo 'Person does not have a middle name';

You can also achieve this with just the ternary operator like so:

echo $person->middleName ?: 'Person does not have a middle name';

But... if the value does not exist (is not set) it will raise an E_NOTICE and is not best practise. If the value is null it will not raise the exception.

Therefore ternary operator to the rescue making this a neat little answer:

echo $person->middleName ?? 'Person does not have a middle name';

Answer 5

If you want to know if a property exists in an instance of a class that you have defined, simply combine property_exists() with isset().

public function hasProperty($property)
{
    return property_exists($this, $property) && isset($this->$property);
}

Answer 6

To check if something exits, you can use the PHP function isset() see php.net. This function will check if the variable is set and is not NULL.

Example:

if(isset($obj->a))
{ 
  //do something
}

If you need to check if a property exists in a class, then you can use the build in function property_exists()

Example:

if (property_exists('class', $property)) {
    //do something
}

Answer 7

Using array_key_exists() on objects is Deprecated in php 7.4

Instead either isset() or property_exists() should be used

reference : php.net

Answer 8

Just putting my 2 cents here.

Given the following class:

class Foo
{
  private $data;

  public function __construct(array $data)
  {
    $this->data = $data;
  }

  public function __get($name)
  {
    return $data[$name];
  }

  public function __isset($name)
  {
    return array_key_exists($name, $this->data);
  }
}

the following will happen:

$foo = new Foo(['key' => 'value', 'bar' => null]);

var_dump(property_exists($foo, 'key'));  // false
var_dump(isset($foo->key));  // true
var_dump(property_exists($foo, 'bar'));  // false
var_dump(isset($foo->bar));  // true, although $data['bar'] == null

Hope this will help anyone

Answer 9

Usually I use kind of custom helper

    /**
     * @param Object $object
     * @param string $property as a string with nested properties 'prop1.nesterdProp.deepvalue'
     * @param mixed $default
     * @return mixed
     */
    function getPropertyOrDefault(Object $object, string $property, $default = null)
    {
        $value = $object;
        $path = explode('.', $property);
        foreach ($path as $prop) {
            if (is_object($value) && property_exists($value, $prop)) {
                $value = $value->{$prop};
            } else {
                return $default;
            }
        }
        return $value;
    }

Keep in mind that if property is empty you will get empty value and no default value.

BTW the similar helper works in JS as well.

Answer 10

Since php8.0 one can use ?? operator as sugar for isset. Keep in mind that that$foo->bar??<what value you want here> will return <what value you want here> if $foo->bar is not set and $foo->bar otherwise, no matter what value $foo->bar has, posible 0, false, '' or other falsy values