String concatenation-php Tutorial

Ask for string concatenation. what I want to achieve is to press this button. if Cat_ID;?> Assume that the value of this ID is 6.
Open http: // localhost/myweb/wp-admin/post-new.php? Cat = 6

I wrote this:
Onclick = "window. location. href = './wp-admin/post-new.php? Cat = Cat_ID;?> '"

The ID value is also obtained, but cannot be spliced. The result access is always:
Http: // localhost/myweb/wp-admin/post-new.php? Cat =


How can I achieve the hybrid splicing of HTML and PHP in this place?

Reply to discussion (solution)

Onclick = "window. location. href = './wp-admin/post-new.php? Cat =

 Cat_ID;?> '"

Changed:

Onclick = "window. location. href = './wp-admin/post-new.php? Cat =

 Cat_ID;?> '"

Add an echo.

Positive solution! Deliver score to hero!