The following line:
以下行：
echo date('d', strtotime('First Saturday August 2015'));
prints 08, which doesn't seem to make any sense because the first occurrence of a day of the week can't be after the 7th.
打印08，这似乎没有任何意义，因为第一次出现的一周不能在7日之后。
Is it a php bug or a php bug or maybe even a php bug? I don't know...
它是一个php bug还是一个php bug，甚至可能是一个php bug？我不知道...
php version: 5.5.19
php版本：5.5.19
3 个解决方案
#1
44
Update #1: explained below the big difference that a simple word like "of" makes, after I investigated a little in the PHP source code.
更新＃1：在我在PHP源代码中稍微调查一下后，解释了一个像“of”这样的简单单词的巨大差异。
Update #2: There actually is a documentation page on PHP manual that explains the formats of dates accepted by strftime(). I just was not aware of it until now. Thanks @Outspaced for providing the link in their answer.
更新＃2：实际上有一个关于PHP手册的文档页面，它解释了strftime（）接受的日期格式。直到现在我才意识到这一点。感谢@Outspaced在他们的回答中提供链接。
For a quick and easy reading skip the section Update #1.
要快速轻松地阅读，请跳过更新＃1部分。
The initial answer:
Indeed,
确实，
echo date('Y-m-d', strtotime('First Saturday August 2015'));
prints:
打印：
2015-08-08
But
但
echo date('Y-m-d', strtotime('First Saturday of August 2015'));
prints the correct date:
打印正确的日期：
2015-08-01
Since strtotime() tries to "understand" English, I guess you and it speak different dialects :-)
由于strtotime（）试图“理解”英语，我想你和它说不同的方言:-)
Update #1:
After some reading in the PHP source code of function strtotime(), I think that it parses First Saturday August 2015 as First Saturday followed by August 2015.
在阅读了函数strtotime（）的PHP源代码之后，我认为它将2015年8月的第一个星期六解析为第一个星期六，然后是2015年8月。
August 2015 is an absolute expression and because there is no indication about the day it produces 2015-08-01 (the 1st of August 2015) which is a reasonable guess (the only one possible, I think).
2015年8月是一个绝对的表达，因为没有迹象表明它生成2015-08-01（2015年8月1日）的那一天是一个合理的猜测（我认为唯一可能的）。
First Saturday is a relative expression. It is relative to an absolute mark provided in the string (August 2015) or as a second parameter of strtotime() and it "shifts" the timestamp of the absolute mark back or forward with some amount.
第一个星期六是相对表达。它相对于字符串中提供的绝对标记（2015年8月）或作为strtotime（）的第二个参数，它以一定的量“向后或向前”移动绝对标记的时间戳。
Putting them together, strtotime() interprets First Saturday August 2015 as First Saturday counting since August 1, 2015 and that is, indeed, August 8, 2015.
将它们放在一起，strtotime（）将2015年8月的第一个星期六解释为自2015年8月1日起的第一个星期六，即2015年8月8日。
On the other hand, First Saturday of August 2015 is parsed using a different rule. One of next, last, previous, this or any ordinal number from first to twelfth, followed by a weekday name (full or abbreviated) and followed by of is parsed as a weekday of the provided month (or the current month if none is provided in the string).
另一方面，使用不同的规则解析2015年8月的第一个星期六。从第一个到第十二个的下一个，最后一个，前一个，这个或任何序号，然后是工作日名称（完整或缩写），然后是of，将其解析为所提供月份的工作日（如果没有提供，则解析为当前月份）在字符串中）。
Update #2
After I found out that the format of the string accepted by strtotime() is actually explained in the PHP documentation, the explanation became more simple. Take a look at the second "Note:" box in the documentation page.
在我发现strtotime（）接受的字符串格式在PHP文档中实际解释后，解释变得更加简单。请查看文档页面中的第二个“注意：”框。
First Saturday August 2015 is explained at item #4 in the note:
2015年8月的第一个星期六在说明中的第4项解释：
"ordinal dayname" does advance to another day.
“序数日名”确实进展到另一天。
First Saturday of August 2015 is explained at item #6 of the note:
2015年8月的第一个星期六在说明的第6项解释：
"ordinal dayname 'of'" does not advance to another day.
“ordinal dayname”的''不会提前到另一天。
The note ends with an entire block of explanation dedicated to the magical word "of".
该笔记以一整段解释结束，专门用于神奇的“of”字样。
#2
12
You need an 'of':
你需要一个'of'：
date('d/m/Y', strtotime('First Saturday of August 2015'))
see the manual: http://docs.php.net/manual/en/datetime.formats.relative.php
参见手册：http：//docs.php.net/manual/en/datetime.formats.relative.php
#3
-2
As stated, PHP didn't quite understand your choice of dialect. If you plan on accepting varied input from your users (not a bad idea) to express a date, I suggest doing some normalization of that user input yourself so that you can submit a predictable format to strtotime.
如上所述，PHP并不十分了解您对方言的选择。如果您计划接受来自用户的不同输入（不是一个坏主意）来表达日期，我建议您自己对该用户输入进行一些规范化，以便您可以向strtotime提交可预测的格式。
#1
44
Update #1: explained below the big difference that a simple word like "of" makes, after I investigated a little in the PHP source code.
更新＃1：在我在PHP源代码中稍微调查一下后，解释了一个像“of”这样的简单单词的巨大差异。
Update #2: There actually is a documentation page on PHP manual that explains the formats of dates accepted by strftime(). I just was not aware of it until now. Thanks @Outspaced for providing the link in their answer.
更新＃2：实际上有一个关于PHP手册的文档页面，它解释了strftime（）接受的日期格式。直到现在我才意识到这一点。感谢@Outspaced在他们的回答中提供链接。
For a quick and easy reading skip the section Update #1.
要快速轻松地阅读，请跳过更新＃1部分。
The initial answer:
Indeed,
确实，
echo date('Y-m-d', strtotime('First Saturday August 2015'));
prints:
打印：
2015-08-08
But
但
echo date('Y-m-d', strtotime('First Saturday of August 2015'));
prints the correct date:
打印正确的日期：
2015-08-01
Since strtotime() tries to "understand" English, I guess you and it speak different dialects :-)
由于strtotime（）试图“理解”英语，我想你和它说不同的方言:-)
Update #1:
After some reading in the PHP source code of function strtotime(), I think that it parses First Saturday August 2015 as First Saturday followed by August 2015.
在阅读了函数strtotime（）的PHP源代码之后，我认为它将2015年8月的第一个星期六解析为第一个星期六，然后是2015年8月。
August 2015 is an absolute expression and because there is no indication about the day it produces 2015-08-01 (the 1st of August 2015) which is a reasonable guess (the only one possible, I think).
2015年8月是一个绝对的表达，因为没有迹象表明它生成2015-08-01（2015年8月1日）的那一天是一个合理的猜测（我认为唯一可能的）。
First Saturday is a relative expression. It is relative to an absolute mark provided in the string (August 2015) or as a second parameter of strtotime() and it "shifts" the timestamp of the absolute mark back or forward with some amount.
第一个星期六是相对表达。它相对于字符串中提供的绝对标记（2015年8月）或作为strtotime（）的第二个参数，它以一定的量“向后或向前”移动绝对标记的时间戳。
Putting them together, strtotime() interprets First Saturday August 2015 as First Saturday counting since August 1, 2015 and that is, indeed, August 8, 2015.
将它们放在一起，strtotime（）将2015年8月的第一个星期六解释为自2015年8月1日起的第一个星期六，即2015年8月8日。
On the other hand, First Saturday of August 2015 is parsed using a different rule. One of next, last, previous, this or any ordinal number from first to twelfth, followed by a weekday name (full or abbreviated) and followed by of is parsed as a weekday of the provided month (or the current month if none is provided in the string).
另一方面，使用不同的规则解析2015年8月的第一个星期六。从第一个到第十二个的下一个，最后一个，前一个，这个或任何序号，然后是工作日名称（完整或缩写），然后是of，将其解析为所提供月份的工作日（如果没有提供，则解析为当前月份）在字符串中）。
Update #2
After I found out that the format of the string accepted by strtotime() is actually explained in the PHP documentation, the explanation became more simple. Take a look at the second "Note:" box in the documentation page.
在我发现strtotime（）接受的字符串格式在PHP文档中实际解释后，解释变得更加简单。请查看文档页面中的第二个“注意：”框。
First Saturday August 2015 is explained at item #4 in the note:
2015年8月的第一个星期六在说明中的第4项解释：
"ordinal dayname" does advance to another day.
“序数日名”确实进展到另一天。
First Saturday of August 2015 is explained at item #6 of the note:
2015年8月的第一个星期六在说明的第6项解释：
"ordinal dayname 'of'" does not advance to another day.
“ordinal dayname”的''不会提前到另一天。
The note ends with an entire block of explanation dedicated to the magical word "of".
该笔记以一整段解释结束，专门用于神奇的“of”字样。
#2
12
You need an 'of':
你需要一个'of'：
date('d/m/Y', strtotime('First Saturday of August 2015'))
see the manual: http://docs.php.net/manual/en/datetime.formats.relative.php
参见手册：http：//docs.php.net/manual/en/datetime.formats.relative.php
#3
-2
As stated, PHP didn't quite understand your choice of dialect. If you plan on accepting varied input from your users (not a bad idea) to express a date, I suggest doing some normalization of that user input yourself so that you can submit a predictable format to strtotime.
如上所述，PHP并不十分了解您对方言的选择。如果您计划接受来自用户的不同输入（不是一个坏主意）来表达日期，我建议您自己对该用户输入进行一些规范化，以便您可以向strtotime提交可预测的格式。