WSOD after restore of SMF directory and database

[jpgreen3]

New interest in my little-used community forum (v2.1 RC 2) revealed an error preventing new registrations.
I decided to revert to a 2.0.13 backup.  I restored the forum root directory (SMF) and a MySQL database backup taken at the same time. 
SMF is running in a sub-directory under WordPress. 

This is the error being returned:
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Fatal error: Uncaught Error: Call to undefined function mysql_connect() in /home/nereus6/public_html/stormmountain.org/smf/Sources/Subs-Db-mysql.php:58 Stack trace: #0 /home/nereus6/public_html/stormmountain.org/smf/Sources/Load.php(2550): smf_db_initiate('localhost', 'nereus6_smf426', 'nereus6_smf426', 'xxxxxx', 'smfho_', Array) #1 /home/nereus6/public_html/stormmountain.org/smf/index.php(72): loadDatabase() #2 {main} thrown in /home/nereus6/public_html/stormmountain.org/smf/Sources/Subs-Db-mysql.php on line 58
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Connecting to the MySQL database should be pretty basic, but I'm clueless - any ideas?

PHP Version 7.1.33 - the link to my phpinfo was disallowed.

[shawnb61]

2.0.13 won't run on php 7.x.

You need to set your php version to something like 5.6.

[jpgreen3]

Thanks - that got me past the WSOD.