PHP中的日期和时间处理函数详解

在 Web 开发中，处理日期和时间是一个常见的任务。PHP 提供了一系列强大的日期和时间处理函数，例如 strtotime、date 和 DateTimeImmutable::createFromFormat 等。

这些函数使得在不同的时间格式之间进行转换，进行日期和时间计算以及格式化输出变得更加便捷。

本文将深入探讨这三个函数的用法和优势。

1. strtotime 函数

strtotime函数用于将人类可读的日期和时间字符串转换为 Unix 时间戳。它可以接受一个日期时间字符串作为参数，并尝试解析它并将其转换为对应的 Unix 时间戳。除了接受基本的日期时间格式外，它还可以理解各种相对时间表达式。以下是strtotime函数的参数和作用：

<span class="token function">strtotime</span><span class="token punctuation">(</span>string <span class="token variable">$datetime</span><span class="token punctuation">,</span> <span class="token operator">?</span>int <span class="token variable">$baseTimestamp</span> <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">:</span> int<span class="token operator">|</span><span class="token boolean">false</span>

• 参数：string $datetime, ?int $baseTimestamp = null
• $datetime：需要解析的日期时间字符串。
• $baseTimestamp：可选参数，表示用于计算相对日期的基础时间戳。
• 返回值：解析成功则返回对应的 Unix 时间戳，解析失败则返回false。

使用strtotime函数时，可以传递各种不同格式的日期时间字符串，包括绝对时间（如 "2023-08-06"、"15:30:00"）以及相对时间（如 "tomorrow"、"next week"）。

函数会尝试根据传入的字符串进行合理的日期时间转换，方便进行时间的计算和比较。

<span class="token keyword">echo</span> <span class="token function">strtotime</span><span class="token punctuation">(</span><span class="token string">"2023-08-06 15:30:00"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token constant">PHP_EOL</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token function">strtotime</span><span class="token punctuation">(</span><span class="token string">"tomorrow"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token constant">PHP_EOL</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token function">strtotime</span><span class="token punctuation">(</span><span class="token string">"+1 day"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token constant">PHP_EOL</span><span class="token punctuation">;</span>

2. date 函数

date函数用于将 Unix 时间戳格式化为所需的日期和时间字符串。它接受一个格式字符串和一个 Unix 时间戳作为参数，然后返回一个格式化后的日期时间字符串。以下是date函数的参数和作用：

<span class="token function">date</span><span class="token punctuation">(</span>string <span class="token variable">$format</span><span class="token punctuation">,</span> <span class="token operator">?</span>int <span class="token variable">$timestamp</span> <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">:</span> string

• 参数：string $format, ?int $timestamp = null
• $format：日期时间格式字符串，其中包含各种格式化选项，用于定义输出的日期时间样式。
• $timestamp：可选参数，表示需要格式化的 Unix 时间戳。默认为time()函数的返回值，即当前的 Unix 时间戳。
• 返回值：根据指定格式返回格式化后的日期时间字符串。

date函数的第一个参数是日期格式字符串，其中包含各种格式化选项，例如 "Y" 代表年份，"m" 代表月份，"d" 代表日期，"H" 代表小时，"i" 代表分钟，"s" 代表秒等。

<span class="token comment" spellcheck="true">// set the default timezone to use.</span>
<span class="token function">date_default_timezone_set</span><span class="token punctuation">(</span><span class="token string">'UTC'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment" spellcheck="true">// Prints something like: Monday</span>
<span class="token keyword">echo</span> <span class="token function">date</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment" spellcheck="true">// Prints something like: Monday 8th of August 2005 03:12:46 PM</span>
<span class="token keyword">echo</span> <span class="token function">date</span><span class="token punctuation">(</span><span class="token string">'l jS \of F Y h:i:s A'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment" spellcheck="true">// Prints: July 1, 2000 is on a Saturday</span>
<span class="token keyword">echo</span> <span class="token string">"July 1, 2000 is on a "</span> <span class="token punctuation">.</span> <span class="token function">date</span><span class="token punctuation">(</span><span class="token string">"l"</span><span class="token punctuation">,</span> <span class="token function">mktime</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2000</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment" spellcheck="true">/* use the constants in the format parameter */</span>
<span class="token comment" spellcheck="true">// prints something like: Wed, 25 Sep 2013 15:28:57 -0700</span>
<span class="token keyword">echo</span> <span class="token function">date</span><span class="token punctuation">(</span><span class="token constant">DATE_RFC2822</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment" spellcheck="true">// prints something like: 2000-07-01T00:00:00+00:00</span>
<span class="token keyword">echo</span> <span class="token function">date</span><span class="token punctuation">(</span><span class="token constant">DATE_ATOM</span><span class="token punctuation">,</span> <span class="token function">mktime</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2000</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

通过组合这些选项，就可以创建出各种不同的日期和时间格式。

3. DateTimeImmutable::createFromFormat 方法

DateTimeImmutable::createFromFormat方法是面向对象的日期和时间处理方式，根据指定的格式将日期字符串解析为DateTimeImmutable对象。

这对于处理不同地区的日期格式或需要更精确解析的日期字符串非常有用。

<span class="token keyword">public</span> <span class="token keyword">static</span> DateTimeImmutable<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">createFromFormat</span><span class="token punctuation">(</span>string <span class="token variable">$format</span><span class="token punctuation">,</span> string <span class="token variable">$datetime</span><span class="token punctuation">,</span> <span class="token operator">?</span>DateTimeZone <span class="token variable">$timezone</span> <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">:</span> DateTimeImmutable<span class="token operator">|</span><span class="token boolean">false</span>

<span class="token function">date_create_immutable_from_format</span><span class="token punctuation">(</span>string <span class="token variable">$format</span><span class="token punctuation">,</span> string <span class="token variable">$datetime</span><span class="token punctuation">,</span> <span class="token operator">?</span>DateTimeZone <span class="token variable">$timezone</span> <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">:</span> DateTimeImmutable<span class="token operator">|</span><span class="token boolean">false</span>

以下是DateTimeImmutable::createFromFormat方法的参数和作用：

• 参数：string $format, string $datetime, ?DateTimeZone $timezone = null
• $format：日期时间格式字符串，用于指定输入的日期时间字符串的格式。
• $datetime：需要解析的日期时间字符串。
• $timezone：可选参数，用于设置解析后的DateTimeImmutable对象的时区。如果不指定，默认为null，表示使用服务器的时区设置。
• 返回值：如果解析成功，则返回一个DateTimeImmutable对象，如果解析失败，则返回false。

使用DateTimeImmutable::createFromFormat方法时，您需要定义一个格式字符串，该格式字符串与输入的日期时间字符串相匹配。

<span class="token variable">$dateString</span> <span class="token operator">=</span> <span class="token string">"06/08/2023"</span><span class="token punctuation">;</span>
<span class="token variable">$format</span> <span class="token operator">=</span> <span class="token string">"d/m/Y"</span><span class="token punctuation">;</span>
<span class="token variable">$dateTime</span> <span class="token operator">=</span> DateTimeImmutable<span class="token punctuation">:</span><span class="token punctuation">:</span><span class="token function">createFromFormat</span><span class="token punctuation">(</span><span class="token variable">$format</span><span class="token punctuation">,</span> <span class="token variable">$dateString</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token variable">$dateTime</span> <span class="token keyword">instanceof</span> <span class="token class-name">DateTimeImmutable</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">echo</span> <span class="token variable">$dateTime</span><span class="token operator">-</span><span class="token operator">></span><span class="token function">format</span><span class="token punctuation">(</span><span class="token string">"Y-m-d"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">// 输出：2023-08-06</span>
<span class="token punctuation">}</span>

总结

在 PHP 中，日期和时间处理是一个常见但复杂的任务。strtotime、date和DateTimeImmutable::createFromFormat这三个函数为我们提供了强大的工具，使得处理不同格式的日期和时间变得更加便捷。

strtotime用于将字符串转换为 Unix 时间戳，date用于将时间戳格式化为可读的字符串，而DateTimeImmutable::createFromFormat则允许更精确地解析日期字符串。

通过熟练掌握这些函数，可以更好地处理和管理日期时间相关的任务，提升 Web 开发效率。