Question

What is the best way to check if a given date – a string d/mm/yyyy is a past?
When I used strtotime(), it didn’t work well, because of non-American notation.
Of course I might deal with the dates as strings and compare substrings, but there has to be a better way.

if((strtotime('now')-strtotime($date)) > 86400) echo $date;

Answer 1

Dates in the m/d/y or d-m-y formats are disambiguated by looking at
the separator between the various components: if the separator is a
slash (/), then the American m/d/y is assumed; whereas if the
separator is a dash (-) or a dot (.), then the European d-m-y format
is assumed.

strtotime() manual

So a simple str_replace('/', '-', $date) should do the trick.