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Validating Dates

5:13 with Alena Holligan

How do we assure that the date is in the correct format and is actually a valid date? In this video, we'll explore one option for validating string formats and checking for a valid date.

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Documentation

explode() Split a string by string

strlen() Get string length

checkdate() Validate a Gregorian date

Regular Expressions

Another option you often see for validating strings, is the use of regular expressions. A regular expression (regex or regexp for short) is a special text string for describing a search pattern. Regular expressions are a great tool to learn. Most applications as well as most programming languages include some form of regular expression matching.

PHP includes a number of Regular Expression Functions. We could use preg_match to match our dates as well.

Example:

if (preg_match('/^(\d{2})\/(\d{2})\/(\d{4})$/', $date, $dateMatch)) {
   if (!checkdate($dateMatch[1], $dateMatch[2], $dateMatch[3])) {
       $error_message = 'Invalid Date';
   }
} else {
   $error_message = 'Invalid Date format';
}

This matches a string that starts with (^) 2 digits (\d{2}), followed by a forward slash (\/), then another 2 digits (\d{2}) followed by another forward slash (\/), and finally 4 digits (\d{4}) at the end($).

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The task form is working and adding values to the database but 0:00

we don't have any data integrity when it comes to dates. 0:04

The project is a drop down and the filtering for integer ensures 0:07

that the time is a number but currently we except anything in the date field. 0:11

We have suggested the format we want, a two-digit month 0:16

followed by a forward slash and a two digit day then another forward slash and 0:21

a four digit year but there's nothing enforcing that format. 0:26

So it's all too easy to add an invalid format whether we're trying to or 0:30

not or even an invalid date. 0:34

Not all months have 31 days. 0:37

So, how do we sure that the date is in the correct format and 0:39

is actually a valid date? 0:43

Let's jump back into work spaces and explore one option. 0:45

In task.php, after we've collected the user data, let's check the date variable. 0:49

First, we need to get each piece of the date so we'll use the explode function. 0:56

Explode takes two parameters, a string delimiter and the string and 1:01

returns an array. 1:06

So let's assign this to a variable dateMatch. 1:07

We use explode, And first the string delimiter. 1:13

The string delimiter determines where the string is split. 1:18

In the case of the date, we're going to use the forward slash 1:22

since each piece of the date should be separated with a forward slash. 1:25

Next we use the date for the string. 1:30

Now let's var dump the dateMatch. 1:35

This will show us what we have so far. 1:43

Now, let's go back to the browser. 1:45

Let's start with the completely invalid date and just type today. 1:48

When we submit the form, we see that the date match is set to a single item array 1:53

with the entire string as the first element. 1:58

Now, let's change this to put in a valid date that's just in the wrong format. 2:02

This is a valid date but not the format we want. 2:11

Now we see that dateMatch is a three item array 2:15

with each piece of the date as a separate element. 2:18

Excellent, just what we want. 2:22

Now, let's start writing the conditional. 2:24

Let's add an elseif to this conditional. 2:27

Elseif count dateMatch does not = 3. 2:38

Then we're going to set our error_message. 2:43

Invalid Date. 2:50

We also want to give this error if the date is not the correct format. 2:53

So, let's check that each piece of the array is the correct link. 2:58

Or, string length. 3:00

DateMatch 0. 3:09

Meaning, our first element is not = to 2 or 3:11

the string length, DateMatch 1. 3:16

Meaning, our second element is not = to 2 and 3:22

also string length, dateMatch 2. 3:28

Our third element is not = to 4. 3:34

And finally, we want to check that the date is actually valid and 3:38

that the user has not entered the day that does not exist. 3:42

For example, day 31 in a month that only has 30 days. 3:46

We can use the checkdate function for this or not checkdate. 3:50

checkdate takes three parameters. 3:58

First the month which is our dateMatch 0. 4:01

And then the day, dateMatch 1 and 4:05

then the year, dateMatch 2. 4:10

Great job. Let's take out the var dump and 4:17

run some tests in the browser. 4:18

When we refresh the page, we see our error for 4:25

the required fields because we check for that first. 4:28

So let's make sure all the fields are filled in. 4:32

Now we see invalid date because the year only has two characters and not four. 4:40

Let's change this to 9/31. 4:46

2016. 4:49

We still see invalid date because 4:52

September does not have 31 days. 4:57

Now let's change this to 8/31. 5:03

This time our date was added because the date is valid, great job. 5:06

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