PHP date to timestamp, specified date converted to timestamp

Programmers who have written php+mysql know that there is a time lag, Unix timestamps and formatted dates are two time representations that we often deal with, Unix timestamp storage, easy processing, but not intuitive, formatted date intuitive, but not as easy to handle as the Unix timestamp, So sometimes it's necessary to convert each other, and here are some ways to convert each other.

one, complete in MySQL
　　
This way in the MySQL query statement conversion, the advantage is not to occupy PHP parser parsing time, fast, the disadvantage is only used in database query, there are limitations.
1. UNIX timestamp converted to date function: From_unixtime ()
General form: Select From_unixtime (1156219870);
2. Date conversion to UNIX timestamp function: Unix_timestamp ()
General form: Select unix_timestamp (' 2006-11-04 12:23:00′);
Example: MySQL Query the number of records on the day:
$sql = "SELECT *" from the message Where date_format (From_unixtime (chattime), '%y-%m-%d ') = Date_format (now (), '%y-%m-%d ') ORDER BY id DESC ";
Of course, you can also choose to convert in PHP, the following is said in PHP conversion.

second, complete in PHP
　　
This way in the PHP program to complete the conversion, the advantage is that the database is not the data can be converted, the scope of the conversion is not limited, the disadvantage is to occupy the parsing time of the PHP parser, the speed is relatively slow.
1. UNIX timestamp converted to date function: Date ()
General form: Date (' y-m-d h:i:s ', 1156219870);
2. Date conversion to UNIX timestamp function: Strtotime ()
General form: Strtotime (' 2010-03-24 08:15:42 ');

php date to timestamp, specified date converted to timestamp

PHP Date-to-timestamp, specified date converted to timestamp, PHP timed task.
These two days to achieve this function:
When a certain condition is reached, let the server send a message to the user, the number is more than one.
Basic idea: Linux timed scan, if you meet the conditions of the user, then send a text message.
But in order to prevent the interruption to the user, the request only during the daytime 8:00-20:00 send text messages, how to get to the daily time interval?
The following code:

Copy CodeThe code is as follows:
<?
$y =date ("Y", Time ());
$m =date ("M", Time ());
$d =date ("D", Time ());
$start _time = mktime (9, 0, 0, $m, $d, $y);
$end _time = mktime (0, 0, $m, $d, $y);
$time = time ();
if ($time >= $start _time && $time <= $end _time)
{
Do something ....
}
?>

PHP date to timestamp, specified date converted to timestamp