PHP - Create html elements

Class_Element.php

<?php
/**
 * Create an element
 */
class Element
{
    private $type;
    private $unaryTagArray = array('area','base','br','col','command','embed','hr','img','input','keygen','link','meta','param','source','track','wbr');
    private $attributes;
    private $innerHtml;
    private $children;

    /**
     * Element constructor.
     * @param $type
     * @param array $attributeArray
     */
    public function __construct($type = null, $attributeArray = array())
    {
        $this->attributes = array();
        if(!is_null($type)){
            $this->type = strtolower($type);
            foreach($attributeArray as $attribute => $value) {
                $this->setAttribute($attribute, $value);
            }
        }else{
            $this-> type = 'temp';
            foreach($attributeArray as $attribute => $value) {
                $this->setAttribute($attribute, $value);
            }
        }
        return $this;
    }

    /**
     * Set an array, can pass an array or a key, value combination
     *
     * @param array|string $attribute
     * @param string $value
     * @return object $this
     */
    public function setAttribute($attribute, $value = "")
    {
        if(!is_array($attribute)) {
            $this->attributes[$attribute] = $value;
        }
        else {
            $this->attributes = array_merge($this->attributes, $attribute);
        }

        return $this;
    }

    /**
     * Get Element Type
     *
     * @return string
     */
    public function getType(){
        return $this->type;
    }

    /**
     * Override/Set Element Type
     *
     * @param string $type
     * @return $this
     */
    public function setType($type){
        $this->type = strtolower($type);

        return $this;
    }

    /**
     * Returns the specific Attribute
     *
     * @param $attribute
     * @return mixed
     */
    public function getAttribute($attribute)
    {
        return $this->attributes[$attribute];
    }

    /**
     * @return array
     */
    function displayAttributes(){
        return $this->attributes;
    }

    /**
     * Remove an attribute from an element
     *
     * @param $attribute
     * @return $this
     */
    function removeAttribute($attribute)
    {
        if(isset($this->attributes[$attribute])) {
            unset($this->attributes[$attribute]);
        }
        return $this;
    }

    /**
     * Clear an Element Attributes
     *
     * Clear all of the element's attributes
     */
    function clearAttributes() {
        $this->attributes = array();
        return $this;
    }

    /**
     * Inject an Element into the current Element
     *
     * @param $object
     * @return $this
     */
    function inject($object)
    {
        if(@get_class($object) == __class__) {
            $this->innerHtml .= $object->build();
        }elseif(is_string($object)){
            $this->innerHtml .= $object;
        }
        return $this;
    }

    /**
     * Set Inline Styling
     *
     * @param string $cssAt
     * @param string $value
     *
     * @return object
     */
    function  setStyle($cssAt,$value){
        //@TODO enhance this functionality to allow additions/modifications and deletion
        $this->setAttribute("style", "$cssAt:$value;");


        return $this;
    }


    /**
     * Set the innerHtml of an element
     *
     * @param object|string $object
     * @return $this
     */
    function content($object)
    {
        $this->innerHtml = $object;
        return $this;
    }

    /**
     * Echoes out the element
     *
     * @return string
     */
    function display()
    {
        echo $this->build();
    }

    /**
     * Builds the element
     *
     * @return string
     */
    function build()
    {
        // Start the tag
        $element = "<".$this->type;
        // Add attributes
        if(count($this->attributes)) {
            foreach($this->attributes as $key => $value) {
                $element .= " ".$key."=\"".$value."\"";
            }
        }
        // Close the element
        if(!in_array($this->type, $this->unaryTagArray)) {
            $element.= ">" . $this->innerHtml . "</".$this->type.">\n";
        }
        else {
            $element.= " />\n";
        }
        return $element;
    }


}