will one php script execute before the next is read?

speeding up my site

[GerBot]

I have a php script that I run in the headers of my webpage.
I need this script to execute before the three others within the body tags do.

My question is:
Will all three of my php scripts run before the first or does my server read the html from top to bottom executing each script when I close the php tags?

[volatilegx]

The PHP scripts will execute in the order they are coded on the page.