Solve PHP strtotime produce invalid date

The strtotime() function is a magical function that allows you to parse a string of English datetime description into a Unix timestamp.

This function is designed to let PHP interpret what timestamp value you want from a string, so it has some faults where it can produce an invalid date.

For example, when you put 31-Feb in the string, strtotime() pushed the date forward to 3-Mar as shown below:

<?php

// 👇 this produce invalid date 
$time = "10:24 AM 31-Feb 2022";
$my_time = strtotime($time);

// 👇 10:24 AM 3-Mar 2022
print date("H:i A j-M Y", $my_time);

But strtotime() will return false when you put a date greater than 31 as follows:

// 👇 put 32 as date
$time = "10:24 AM 32-Feb 2022";
$my_time = strtotime($time);

// 👇 bool(false)
var_dump ($my_time);

Most often, the behavior that you want from strtotime() is to return false when you put an invalid date such as 30-Feb or 31-Feb.

Since strtotime() doesn’t have a built-in date validation, you need to do it yourself.

To validate strtotime() date, you need to transform the Unix timestamp back to a date string and see if it matches the original date.

You can use the date() function to format the Unix timestamp as a date string.

Consider the example below:

// 👇 use strtotime()
$time = "10:24 AM 31-Feb 2022";
$my_time = strtotime($time);

// 👇 put strtotime back as date string
$my_time = date("H:i A j-M Y", $my_time);

// 👇 compare original date and strtotime date
if ($time === $my_time) {
    print "Date is VALID";
} else {
    print "Date is INVALID";
}

Put the date format of your original date string as the first argument of the date() function.

By comparing the date strings, you can check if the strtotime() function returns a valid date.

This also works for leap year February dates as shown below:

// 👇 check for 29-Feb 2020
$time = "29-Feb 2020";
$my_time = strtotime($time);

$my_time = date("j-M Y", $my_time);

if ($time === $my_time) {
    print "$time is VALID";
} else {
    print "$time is INVALID";
}

print "\n";

// 👇 Do another round for 29-Feb 2021
$time = "29-Feb 2021";
$my_time = strtotime($time);

$my_time = date("j-M Y", $my_time);

if ($time === $my_time) {
    print "$time is VALID";
} else {
    print "$time is INVALID";
}

The output will be:

29-Feb 2020 is VALID
29-Feb 2021 is INVALID

Now you’ve learned how to handle the PHP strtotime() function producing an invalid date. Very nice! 👍