src/UriTemplates/Parsers/AstNode.php
public function addChild(AstNode $node): AstNode
    {
        $node->parent = $this;
        $this->children[] = $node;

        return $this;
    }
public function addChild(AstNode $node): AstNode
    {
        $node->parent = $this;
        $this->children[] = $node;

        return $this;
    }
Adds a child to this node

@param AstNode $node The child to add
@return AstNode Returns this for chaining