Learning lesson here: Never trust the PHP documentation. Test everything!$position does not work as described, at least in PHP 7. After parsing without errors, it does not contain -1.You can still use it to set the parsing start character position, but not necessarily whether any errors occurred.To test for errors, replace my $nPosition test code in the other note with:<?php // Check if errors$bError = intl_is_failure(datefmt_get_error_code(oIDF));// If no errorif(!$bError){ // Use 'tm_hour' and 'tm_min' from the $aTime array for checking against other time values ...}else{ // Invalid string ...}?>

You can use datefmt_localtime to convert a user's time string, input using their locale's script, into standard numbers for checking, using a simple HTML input element.This avoids using clunky HTML select elements formatted with hour and minute options in the locale's script to capture user input.<?php// Specify locale of user$sLocale = 'en-us'; // US English user$sLocale = 'ar-ye'; // Yemen Arab user// Create a date formatter for the user's locale$oIDF = datefmt_create($sLocale, IntlDateFormatter::NONE, IntlDateFormatter::SHORT);// Simulate a user's time input string$sTime = datefmt_format($oIDF, ['tm_hour'=>15, 'tm_min'=>25]);// For a US English user, $sTime = '3:25 PM'// For a Yemen Arab user, $sTime = '٣:٢٥ م'// Specify datefmt_locale parsing start at the beginning of the user input$nPosition = 0;// Convert input time string to array of standard numeric values, as per localtime() output (http://php.net/manual/en/function.localtime.php)$aTime = datefmt_localtime($oIDF, $sTime, $nPosition);// If no errors, $nPosition set to -1 after parsing, else character position of error// If valid stringif($nPosition = -1){ // Use 'tm_hour' and 'tm_min' from the $aTime array for checking against other time values ...}else{ // Invalid string ...}?>