NullPointerException

warning off by default experimental

Group: Probable bugs · PhpStorm name: NullPointerExceptionInspection

A value that may be null (nullable object parameter, nullable local variable, call declared to return ?T/void) is dereferenced — property or method access, array access, invocation, clone, or passed to a parameter that rejects null — without a preceding null check. At runtime this is an "call to a member function on null"-style error.

Disabled by default (experimental upstream).

Example

<?php
class Node
{
    public $value;
    public function next(): ?Node { return null; }
    public function take(Node $n) {}
    public function walk(?Node $head, Node $tail = null, ?int $count = null, Node $plain, $loose = null)
    {
        $head->value = 1;
        $head();
        if ($head === null) {
            return;
        }
        $head->value = 2;

        $x = clone $tail;
        $this->take($tail);
        echo $tail->value ?? 'none';
        if (isset($tail->value['a'])) {}
        if ($tail) {
            $tail->value = 3;
        }
        $plain->value = 4;
        $loose->value = 5;
        $count++;
    }

    public function chain()
    {
        $this->next()->next();
        if ($this->next() != null) {
            $this->next()->next();
        }
        $n = $this->next();
        $n->next();
        $n['k'];
        $n = new Node();
        $n->value = 0;

        /** @var Node $m */
        $m = $this->next();
        $m->value = 1;

        $cursor = $this->next();
        while ($cursor !== null) {
            $cursor = $cursor->next();
        }

        $probe = $this->next();
        $probe->value = 1;
        $probe = $probe->next();
    }

    public function refill(Node $left = null, ?Node $right, Node $up = null)
    {
        $left = $left ?: null;
        $left->value = 1;

        $right = $right ?? null;
        $right->next();

        $up = $up->next();
    }

    /** @param Node[] $list */
    public function rewind(array $list)
    {
        foreach ($list as $item) {
            $item = $item->next();      // declaring statement of local $item: right side exempt (E4)
            $item->value = 1;
        }
    }

    public function guarded(?Node $a, ?Node $b, ?Node $c)
    {
        static::assertNotNull($a);
        Verify::that($b)->isObject()->notNull();
        $this->that($c)->notNull();

        return [$a->value, $b->value, $c->value];
    }
}

function visit(?Node $item) {
    \Assert\Assertion::notNull($item);
    return $item->value;
}

Reported:

• line 9: Possible null dereference.
• line 10: Possible null dereference.
• line 16: Possible null dereference.
• line 17: Possible null dereference.
• line 30: Possible null dereference.
• line 35: Possible null dereference.
• line 36: Possible null dereference.
• line 50: Possible null dereference.
• line 51: Possible null dereference.
• line 57: Possible null dereference.
• line 60: Possible null dereference.
• line 62: Possible null dereference.
• line 70: Possible null dereference.

Configure

In custos.json:

{
  "rules": {
    "NullPointerException": {
      "enabled": true
    }
  }
}

Suppress

Before the statement or declaration (or the first statement of the file), either of:

// @custos-ignore NullPointerException

/**
 * @noinspection NullPointerExceptionInspection
 */