How do I understand variable references?

{Code ...} at @ 1, $ query is assigned the query attribute of $ dataProvider. At @ 2, $ query adds some query conditions. Excuse me, at @ 3, $ how does the query attribute of dataProvider have the conditions added by $ query at @ 2 ?...

public function search($params){    $query = Post::find();    $dataProvider = new ActiveDataProvider([        # @1        'query' => $query,    ]);    # @2    $query->andFilterWhere(['id' => $this->id]);    $query->andFilterWhere(['like', 'title', $this->title])          ->andFilterWhere(['like', 'creation_date', $this->creation_date]);    # @3    return $dataProvider;}

At @ 1, $ query is assigned the query attribute of $ dataProvider;
At @ 2, $ query adds some query conditions;

In@3Where, how does the query attribute of $ dataProvider have the conditions added by $ query at @ 2?

Code Source

Reply content:

public function search($params){    $query = Post::find();    $dataProvider = new ActiveDataProvider([        # @1        'query' => $query,    ]);    # @2    $query->andFilterWhere(['id' => $this->id]);    $query->andFilterWhere(['like', 'title', $this->title])          ->andFilterWhere(['like', 'creation_date', $this->creation_date]);    # @3    return $dataProvider;}

At @ 1, $ query is assigned the query attribute of $ dataProvider;
At @ 2, $ query adds some query conditions;

In@3Where, how does the query attribute of $ dataProvider have the conditions added by $ query at @ 2?

Code Source

See http://php.net/manual/en/language.oop5.references.php

In php5, an object variable no longer saves the value of the entire object. Only saves an identifier to access the real object content.

class A{    public $foo = 1;}$a = new A;$b = $a;echo $b->foo; # 1$a->foo = 2;echo $b->foo; # 2