src/EntityQueryBuilder.php
public function expr()
    {
        if (!($this->expr instanceof Query\Expr)) {
            $this->expr = new Query\Expr;
        }

        return $this->expr;
    }
public function expr()
    {
        if (!($this->expr instanceof Query\Expr)) {
            $this->expr = new Query\Expr;
        }

        return $this->expr;
    }
Gets an ExpressionBuilder used for object-oriented construction of query expressions.
This producer method is intended for convenient inline usage. Example:

<code>
$qb = $em->createQueryBuilder();
$qb
->select('u')
->from('User', 'u')
->where($qb->expr()->eq('u.id', 1));
</code>

For more complex expression construction, consider storing the expression
builder object in a local variable.

@return Query\Expr