Php reads the database content and then determines the user's registration time. How long will it take to automatically send an email?

Php reads the database content and determines the user's registration time. How long will it take to automatically send an email for reference? For example, the registration time and user name will be called after running, and the user will be automatically sent over 1 month of registration time: & lt; user name & gt; hello, you are at & lt; registration time & gt; register for this site. it has been a month since now. php has read the database content and then determined the user's registration time. an email is automatically sent more than long.
Can I provide a reference?
For example, the registration time and user name will be called after running, and the registration time later than one month will be automatically sent
User: <用户名>
Hello, You <注册时间> It has been a month since I registered this site. thank you for your support.
If you have already sent a message that is not repeated

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This is a very simple thing. if you don't, you still won't, if someone else gives you the code.

Search the database list based on the conditions.
Send emails in the array of the loop list
Save the successfully sent User name list to the table or ID

If you don't know anything, don't do such a "complicated" thing first.
Your questions cannot be answered.

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1. find phpmailer
2. easy time judgment.
3. add a field to identify whether to send. It's not hard.
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$ Array = array ('passerby a' => array ('mail' => 'test1 @ 21cn.com ', 'regtime' => '2017-12-30 12:22:22 '), 'Passers-by B '=> array ('mail' => 'test1 @ 21cn.com', 'regtime' => '2017-12-30 12:22:22 '), 'passby' => array ('mail' => 'test1 @ 21cn.com ', 'regtime' => '2017-12-30 12:22:22 '));

Foreach ($ array as $ key => $ value ){
$ Sendmail-> sendto ($ value ['mail']);
$ Sendmail-> title ('expiration notification ');
$ RegTime = $ value ['regtime'];
$ MailText ="
User: {$ key}
Hello, you have registered this site at {$ regTime}. it has been a month since now. thank you for your support.
";
$ Sendmail-> text ($ mailText );
}
// Update data after sending
$ SQL = "UPDATE member SET send = 1 WHERE id IN (.....)"
Mysql_query ($ SQL );

// This is an example. you can see it clearly. sendmail is also an example. for details, see the reference of the relevant instance.
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Discussion

Reference:

1. find phpmailer
2. easy time judgment.
3. add a field to identify whether to send. It's not hard.

Is there a single php?