我在我正在处理的项目时遇到了一些问题，并在我注意到一些错误后决定更改我的 php 设置。
我更改了设置以显示错误（希望我现在没有）
Warning: date(): It is not safe to rely on the system's timezone settings.
You are *required* to use the date.timezone setting or the
date_default_timezone_set() function. In case you used any of those
methods and you are still getting this warning,
you most likely misspelled the timezone identifier.
We selected 'Europe/Berlin' for 'CET/1.0/no DST' instead in
在对Google进行了一些研究之后，在这里我发现我必须设置默认时区，我也决定制作一个表单，用户可以在其中选择时间设置
<select name="timez">
<option value="<?php echo $timez ?>"><?php echo $timez ?></option>
<option value="Pacific/Midway">(GMT-11:00) Midway Island, Samoa</option>
<option value="America/Adak">(GMT-10:00) Hawaii-Aleutian</option>
<option value="Etc/GMT+10">(GMT-10:00) Hawaii</option>
<option value="Pacific/Marquesas">(GMT-09:30) Marquesas Islands</option>
<option value="Pacific/Gambier">(GMT-09:00) Gambier Islands</option>
<option value="America/Anchorage">(GMT-09:00) Alaska</option>
<option value="America/Ensenada">(GMT-08:00) Tijuana, Baja California</option>
<option value="Etc/GMT+8">(GMT-08:00) Pitcairn Islands</option>
<option value="America/Los_Angeles">(GMT-08:00) Pacific Time (US & Canada)</option>
<option value="America/Denver">(GMT-07:00) Mountain Time (US & Canada)</option>
<option value="America/Chihuahua">(GMT-07:00) Chihuahua, La Paz, Mazatlan</option>
<option value="America/Dawson_Creek">(GMT-07:00) Arizona</option>
<option value="America/Belize">(GMT-06:00) Saskatchewan, Central America</option>
<option value="America/Cancun">(GMT-06:00) Guadalajara, Mexico City, Monterrey</option>
<option value="Chile/EasterIsland">(GMT-06:00) Easter Island</option>
<option value="America/Chicago">(GMT-06:00) Central Time (US & Canada)</option>
<option value="America/New_York">(GMT-05:00) Eastern Time (US & Canada)</option>
<option value="America/Havana">(GMT-05:00) Cuba</option>
<option value="America/Bogota">(GMT-05:00) Bogota, Lima, Quito, Rio Branco</option>
<option value="America/Caracas">(GMT-04:30) Caracas</option>
<option value="America/Santiago">(GMT-04:00) Santiago</option>
<option value="America/La_Paz">(GMT-04:00) La Paz</option>
<option value="Atlantic/Stanley">(GMT-04:00) Faukland Islands</option>
<option value="America/Campo_Grande">(GMT-04:00) Brazil</option>
<option value="America/Goose_Bay">(GMT-04:00) Atlantic Time (Goose Bay)</option>
<option value="America/Glace_Bay">(GMT-04:00) Atlantic Time (Canada)</option>
<option value="America/St_Johns">(GMT-03:30) Newfoundland</option>
<option value="America/Araguaina">(GMT-03:00) UTC-3</option>
<option value="America/Montevideo">(GMT-03:00) Montevideo</option>
<option value="America/Miquelon">(GMT-03:00) Miquelon, St. Pierre</option>
<option value="America/Godthab">(GMT-03:00) Greenland</option>
<option value="America/Argentina/Buenos_Aires">(GMT-03:00) Buenos Aires</option>
<option value="America/Sao_Paulo">(GMT-03:00) Brasilia</option>
<option value="America/Noronha">(GMT-02:00) Mid-Atlantic</option>
<option value="Atlantic/Cape_Verde">(GMT-01:00) Cape Verde Is.</option>
<option value="Atlantic/Azores">(GMT-01:00) Azores</option>
<option value="Europe/Belfast">(GMT) Greenwich Mean Time : Belfast</option>
<option value="Europe/Dublin">(GMT) Greenwich Mean Time : Dublin</option>
<option value="Europe/Lisbon">(GMT) Greenwich Mean Time : Lisbon</option>
<option value="Europe/London">(GMT) Greenwich Mean Time : London</option>
<option value="Africa/Abidjan">(GMT) Monrovia, Reykjavik</option>
<option value="Europe/Amsterdam">(GMT+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna</option>
<option value="Europe/Belgrade">(GMT+01:00) Belgrade, Bratislava, Budapest, Ljubljana, Prague</option>
<option value="Europe/Brussels">(GMT+01:00) Brussels, Copenhagen, Madrid, Paris</option>
<option value="Africa/Algiers">(GMT+01:00) West Central Africa</option>
<option value="Africa/Windhoek">(GMT+01:00) Windhoek</option>
<option value="Asia/Beirut">(GMT+02:00) Beirut</option>
<option value="Africa/Cairo">(GMT+02:00) Cairo</option>
<option value="Asia/Gaza">(GMT+02:00) Gaza</option>
<option value="Africa/Blantyre">(GMT+02:00) Harare, Pretoria</option>
<option value="Asia/Jerusalem">(GMT+02:00) Jerusalem</option>
<option value="Europe/Minsk">(GMT+02:00) Minsk</option>
<option value="Asia/Damascus">(GMT+02:00) Syria</option>
<option value="Europe/Moscow">(GMT+03:00) Moscow, St. Petersburg, Volgograd</option>
<option value="Africa/Addis_Ababa">(GMT+03:00) Nairobi</option>
<option value="Asia/Tehran">(GMT+03:30) Tehran</option>
<option value="Asia/Dubai">(GMT+04:00) Abu Dhabi, Muscat</option>
<option value="Asia/Yerevan">(GMT+04:00) Yerevan</option>
<option value="Asia/Kabul">(GMT+04:30) Kabul</option>
<option value="Asia/Yekaterinburg">(GMT+05:00) Ekaterinburg</option>
<option value="Asia/Tashkent">(GMT+05:00) Tashkent</option>
<option value="Asia/Kolkata">(GMT+05:30) Chennai, Kolkata, Mumbai, New Delhi</option>
<option value="Asia/Katmandu">(GMT+05:45) Kathmandu</option>
<option value="Asia/Dhaka">(GMT+06:00) Astana, Dhaka</option>
<option value="Asia/Novosibirsk">(GMT+06:00) Novosibirsk</option>
<option value="Asia/Rangoon">(GMT+06:30) Yangon (Rangoon)</option>
<option value="Asia/Bangkok">(GMT+07:00) Bangkok, Hanoi, Jakarta</option>
<option value="Asia/Krasnoyarsk">(GMT+07:00) Krasnoyarsk</option>
<option value="Asia/Hong_Kong">(GMT+08:00) Beijing, Chongqing, Hong Kong, Urumqi</option>
<option value="Asia/Irkutsk">(GMT+08:00) Irkutsk, Ulaan Bataar</option>
<option value="Australia/Perth">(GMT+08:00) Perth</option>
<option value="Australia/Eucla">(GMT+08:45) Eucla</option>
<option value="Asia/Tokyo">(GMT+09:00) Osaka, Sapporo, Tokyo</option>
<option value="Asia/Seoul">(GMT+09:00) Seoul</option>
<option value="Asia/Yakutsk">(GMT+09:00) Yakutsk</option>
<option value="Australia/Adelaide">(GMT+09:30) Adelaide</option>
<option value="Australia/Darwin">(GMT+09:30) Darwin</option>
<option value="Australia/Brisbane">(GMT+10:00) Brisbane</option>
<option value="Australia/Hobart">(GMT+10:00) Hobart</option>
<option value="Asia/Vladivostok">(GMT+10:00) Vladivostok</option>
<option value="Australia/Lord_Howe">(GMT+10:30) Lord Howe Island</option>
<option value="Etc/GMT-11">(GMT+11:00) Solomon Is., New Caledonia</option>
<option value="Asia/Magadan">(GMT+11:00) Magadan</option>
<option value="Pacific/Norfolk">(GMT+11:30) Norfolk Island</option>
<option value="Asia/Anadyr">(GMT+12:00) Anadyr, Kamchatka</option>
<option value="Pacific/Auckland">(GMT+12:00) Auckland, Wellington</option>
<option value="Etc/GMT-12">(GMT+12:00) Fiji, Kamchatka, Marshall Is.</option>
<option value="Pacific/Chatham">(GMT+12:45) Chatham Islands</option>
<option value="Pacific/Tongatapu">(GMT+13:00) Nuku'alofa</option>
<option value="Pacific/Kiritimati">(GMT+14:00) Kiritimati</option>
</select>
将数据放入数据库后，我尝试回显结果，它显示完美。
我遇到了这行代码的问题，我不确定为什么它不起作用，这可能吗？
<?
date_default_timezone_set('$timez');
?>
您使用的是单引号。把它们拿出来就行了。它将$timez视为文字字符串
date_default_timezone_set($timez);