Magento2- Display Static Block in Phtml file & CMS page

In XML File:

<referenceContainer name="content">
<block class="Magento\Cms\Block\Block" name="block_identifier">
<arguments>
<argument name="block_id" xsi:type="string">block_identifier</argument>
</arguments>
</block>
</referenceContainer>

In Phtml File:

<?php echo $block->getLayout()->createBlock('Magento\Cms\Block\Block')->setBlockId('block_identifier')->toHtml();?>
 

<?php echo $this->getLayout()->createBlock("Magento\Newsletter\Block\Subscribe")->setTemplate("Magento_Newsletter::subscribe.phtml")->toHtml();?> 

in CMS Content:

{{block class="Magento\\Cms\\Block\\Block" block_id="block_identifier"}}