PHP Syntax Highlighting Broken

Dear All,
I have a PHP program file that all of a sudden has lost its syntax highlighting. If I open a new in memory blank php file and copy the contents of the "broken" PHP file into it, the syntax highlighting reappears. If I overwrite the "broken" PHP file with the new in memory copy, the syntax highlighting stays active, for the current PSPAD editing session.

However closing PSPAD down and reopening the project, the syntax highlighting disappears from that file on reopening.

Any ideas on how to fix?

I am afraid I don't understand.
When you open PHP file, there is no syntax highlighted? In this case is possible your file size exceeded limit for highlighting. Go to program settings / Direct edit button.
Find and change value of HLUpToSize e.g. to 1000000 (size in bytes)

In case your file is highlighted with another highlighter, there can be several reasons:
1. you changed highlighter and PSPad remember it. Change it back to PHP
2. file is highlighter with HTML multihighlighter
3. you assign PHP (or your file) extension to another highlighter. Look on statusbar for syntax name. Go to highlighter settings, choose highlighter from statusbar and remove extension on the second tab

Thanx,
That fixed the problem