How can I implement Method Chaining in PHP 5.x? - php

Question

I have the following class written for PHP 5.4.x. Should this work as I expect?
class SqlBuilder {
private $dbTable;
private $action;
private $data;
private $clause;
public function toString() {
// $sql = generate sql string
// [...]
return $sql;
}
[...]
public function setClause($clause) {
$this->clause = $clause;
}
public function setDbTable($dbTable) {
$this->dbTable = $dbTable;
}
public function setAction($action) {
$this->action = $action;
}
}
$sql = (new \dbal\SqlBuilder())
->setAction($this->action)
->setClause($this->clause)
->setDbTable($this->dbTable)
->toString();
I am expecting to be able to access all of my setter methods. Instead I see the following error:
Fatal error: Call to a member function toString() on a non-object )
This seems to work:
$builder= new \dbal\SqlBuilder();
$builder->setAction($this->action)
$builder->setClause($this->clause)
$builder->setDbTable($this->dbTable)
$sql = $builder->toString();
But I know that this works as well:
class Foo
{
public $a = "I'm a!";
public $b = "I'm b!";
public $c;
public function getB() {
return $this->b;
}
public function setC($c) {
$this->c = $c;
return $this;
}
public function getC() {
return $this->c;
}
}
print (new Foo)
->setC($_GET["c"])
->getC(); // I'm c!
I've used this style of syntax in Javascript before. Is there a way to make it work in PHP?

Answer 1

What you are asking about is called method chaining. In order for it to work the way you want, each method call needs to return a reference to the object that you are calling. So,
->setAction($this->action)
// needs to return $this; so that
->setClause($this->clause)
// knows what to operate upon and in turn needs to return $this; so that
->setDbTable($this->dbTable)
// can do the same
Try :
public function setClause($clause) {
$this->clause = $clause;
return $this;
}
public function setDbTable($dbTable) {
$this->dbTable = $dbTable;
return $this;
}
public function setAction($action) {
$this->action = $action;
return $this;
}