Take a script, call it /test.php. Let's track how many actual page loads happen per visual, user-experienced page load.
# Count = 1
test.php?v=1
# Count = 2
test.php?v=1
# Count = 4 (???)
test.php?v=2
# Count = 7 (???)
test.php?v=1
# Count = 8
test.php?v=1
# Count = 10 (???)
test.php?v=3
# Count = 11
test.php?v=3
# Count = 15 (???)
test.php?v=2
# Count = 18 (???)
test.php?v=1
In Chrome, the number of loads is as expected - 1, 2, 3, then 4, 5, etc.
Furthermore, Safari behaves as expected - as Chrome behaves - if you do this in a Private Window.
Why is Safari behaving like this? Is there contribution from something else in the stack, such as from Apache or PHP?
Apache log of a smaller test case. (!!!) test.php?v=3 is logged despite not willfully being requested by me.
# Procedure
test.php?v=1
test.php?v=1
test.php?v=2
# Apache Log of above page loads with IP redacted.
REDACTED_IP - - [20/Apr/2020:11:35:26 +0000] "GET /test.php?v=1 HTTP/1.1" 200 8875 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15"
REDACTED_IP - - [20/Apr/2020:11:35:28 +0000] "GET /test.php?v=1 HTTP/1.1" 200 5141 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15"
REDACTED_IP - - [20/Apr/2020:11:35:42 +0000] "GET /test.php?v=3 HTTP/1.1" 200 8876 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15"
REDACTED_IP - - [20/Apr/2020:11:35:42 +0000] "GET /test.php?v=2 HTTP/1.1" 200 5141 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15"
REDACTED_IP - - [20/Apr/2020:11:35:43 +0000] "GET /test.php?v=2 HTTP/1.1" 200 5705 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.5 Safari/605.1.15"
Here are the stripped-down contents of test.php. Requires Redis and PHP-Redis, as I'm using that for a quick visual. You can of course use Apache logs instead if you wish, or any other way to quickly see the number of times the script has been executed.
<?php
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
echo $redis->incr('counter');