Method Chaining Returns Null

Why This Happens

Method chaining requires each method to return an object that the next method can be called on. If any method in the chain returns null or void, the next call will fail with a 'call to member function on null' error. This is common with builder patterns where a method forgets to return $this.

The Problem

class QueryBuilder {
    public function select(string $columns): self {
        $this->select = $columns;
        // Missing return $this!
    }
    public function where(string $condition): self {
        $this->where = $condition;
        return $this;
    }
}
$builder = new QueryBuilder();
$builder->select('*')->where('id = 1'); // select() returns null

The Fix

class QueryBuilder {
    public function select(string $columns): self {
        $this->select = $columns;
        return $this; // Enable chaining
    }
    public function where(string $condition): self {
        $this->where = $condition;
        return $this;
    }
}

Step-by-Step Fix

1. 1

   Find the broken link

   Identify which method in the chain returns null by breaking the chain into separate calls and checking each return value.

2. 2

   Add return $this

   Ensure every chainable method explicitly returns $this at the end.

3. 3

   Use the nullsafe operator

   In PHP 8+, use ?-> for optional chaining: $builder?->select('*')?->where('id = 1') to gracefully handle null.