需要帮助才能理解php函数

Question

Need help understanding why this doesn't work. I have a text that's only visible on a given start date and time and gets removed on ended date and time.

This is the code I am using that works just fine. The text is visible for a month without problems:

<?php 
     if ( date('Y/m/d H:i') >= "2017/04/06 08:00" && 
          date('Y/m/d H:i') <= "2017/05/06 20:00" ) { 
         echo "$text_1"; 
     } else { 
         echo "$text_2"; 
     }
?>

This is how I would like to be able write the date but it doesn't work as it supposed to:

<?php 
     if ( date('d/m/Y H:i') >= "06/04/2017 08:00" && 
          date('d/m/Y H:i') <= "06/05/2017 20:00" ) { 
         echo "$text_1"; 
     } else { 
         echo "$text_2"; 
     }
?>

It doesn't take into account the month or year. Why is that? This would only show the text for one day and not for a month.

Answer 1

Change date into timestamp and then compare. Format will not matter

if ( strtotime(date("Y-m-d H:i")) >= strtotime("06/04/2017 08:00") && 
    strtotime(date("Y-m-d H:i")) <= strtotime("06/05/2017 20:00" )) { 
    echo "$text_1"; 
} 
else { 
    echo "$text_2"; 
}

Its does not matter the formate now whether "Ymd H:i" or d/m/YH:i . You can do any formate.

You can also do as follows

if ( strtotime(date("d/m/Y H:i")) >= strtotime("06/04/2017 08:00") && 
    strtotime(date("d/m/Y H:i")) <= strtotime("06/05/2017 20:00" )) { 
    echo "aaa"; 
} 
else { 
    echo "bbb"; 
}

The date format really does not matter, when ever you try to compare dates, Convert that in seconds and then compare .
Just take a lot at strtotime() method and do examples and see.

Answer 2

The problem is that you compare strings using >= and <= which is not possible in most cases.

Here's what PHP does when executing the comparison date('Y/m/d H:i') >= "2017/04/06 08:00" :

First, the date() function is executed, which returns a string like "2017/04/23 12:51"

Since >= can only compare numbers, both strings are then implicitly casted into double . For this, PHP uses the strtod function. This function parses a string from left to right. If the first thing it finds (except for whitespace) is a number/ infinity / NAN , this number is returned. As soon as strtod finds a non-numeric character, the rest of the string is ignored. If strtod does not find a number, it returns 0 .

In this case, strtod returns only the year because it does not understand what a / means, and therefore ignores everything after the year.

---

If you want to compare dates properly, you have to use timestamps . To get the current timestamp, PHP offers the time() function.

---

• Unix strtod() Reference
• PHP time() Reference