PHP 里的三种文件时间表述方式 | 相关函数filemtime()、date()、diffForHumans()

1. filemtime()

作用: 获取文件的修改时间。

语法：

filemtime(string $filename): int|false
/* Gets the modification time. Returns the time when the data blocks of a file were being written to, that is, the time when the content of the file was changed.
:param filename: path to the file.
:return: the time the file was last modified, or FALSE on failure. The time is returned as a Unix timestamp, which is suitable for the date() function.
:errors/exceptions: upon failure, an E_WARNING is emitted.
*/

e.g.

<?php 
　　echo "last updated:";
　　echo filemtime('contact.txt'); 
?>

注意：

1. 每个文件系统的时间分辨率可能会不同。

2. 函数的结果将被存入缓存(cached)。

3. 从PHP 5.0.0开始，此函数也可以用于一些URL wrappers。

效果：

----------------------------------------------------

Reference:

1. https://www.php.net/manual/en/function.filemtime.php

缺点：

该函数返回的是Unix Time Stamp时间戳类型，以秒为单位追溯时间(reference: https://www.unixtimestamp.com/)，不够直观。

解决方法：

用date()函数指定输出的时间格式(reference: https://www.php.net/manual/en/function.date.php

 

2. date()

作用：输出指定格式的时间。

语法：

date(string $format[, int $timestamp = time()]) : string
/* Format a local time/date. Returns a string formatted according to the given format string using the given integer timestamp or the current time if no timestamp is given. 
:param format: format accepted by DateTimeInterface::format().
:timestamp: The optional timestamp parameter is an int Unix timestamp that defaults to the current local time if a timestamp is not given. 
:return: a formatted date string. 
:errors/exceptions: if a non-numeric value is used for timestamp, FALSE is returned and an E_WARNING level error is emitted. Every call to a date/time function will generate a E_NOTICE if the time zone is not valid, and/or a E_STRICT or E_WARNING message if using the system settings or the TZ environment variable. 
*/

e.g.

<?php 
　　echo "last updated:";
　　echo date ("F d Y H:i:s", filemtime('contact.txt')); 
?>

注意：

1. timestamp是一个可选的函数，如用户未指定，则其值等于系统的当前时间，即等于函数time()的返回值。

效果：

----------------------------------------------------

Reference:

1. https://www.php.net/manual/en/function.date.php

 

3. diffForHumans()

作用：用文字方式表述时间。

e.g.

<?php 
　　require "libs/Carbon.php";
　　use Carbon\Carbon;
  
　　$ts = filemtime($filename); // 创建时间戳
　　$carb = Carbon::createFromTimestamp($ts); // 创建Carbon对象
　　echo "last updated:";
　　echo $carb->diffForHumans(); // 生成文字内容
?>

注意：

1. 引用前需先下载库文件Carbon.php(https://raw.githubusercontent.com/briannesbitt/Carbon/1.17.0/src/Carbon/Carbon.php)。Carbon是继承自PHP DateTime()的子类，但比后者提供了更丰富、更语义化的API(reference: https://learnku.com/articles/5577/the-diffforhumans-method-of-carbon。

效果：