<?php
$config = '[log]
log_writers[] = "file"
log_writers[] = "screen"

[General]
maintenance_mode = 0
enable_browser_archiving_triggering = 0
enable_sql_optimize_queries = 0
force_ssl = 1';

echo preg_match_all( '/^maintenance_mode[ \t]*=[ \t]*\d$/m', $config ) . PHP_EOL;

echo preg_match_all( '/^maintenance_mode[ \t]*=[ \t]*\d\s$/m', $config );