You can include custom PHP code in your pages in a couple ways…
Including code at the page configuration level
Step 1: Create your code block
In this case, I recommend using a plain text block for your code. In the Add Content menu, select Block > Basic > Text Block.
Add you code as the text block content.
Be sure to wrap your code in the correct code section tags!
Step 2: Add your code to the page configuration
Edit the desired page.
Select the Configure tab.
Select the php output.
In the CODE region, use the asset selector to select your code block.
You can leave the format selector empty