In this previous tutorial we created a simple registration form.
Websites often require a specific strength for a password. In this lesson we will use RegEx to test the password strength.
For our password strength we will specify the following requirements:
a minimum of 8 characters
at least one uppercase letter
at least one number (digit)
at least one of the following special characters !@#$%^&*-
We will start with a basic PHP file and assume that the user has already input their password which we are storing in the variable $password.
Line 2: we have stored the user password in the variable $password
Line 3: this is where we will define the pattern we need to match
Lines 4 to 8: we will test if the password is strong enough and output a message
Line 4: we need to test if the password is strong enough. At the moment we just have pseudo code. We will use a PHP function called preg_match()
The preg_match() function
Currently we just have some psuedo code on line 4. We will use the preg_match function to check if the password matches the defined pattern as follows:
Now we need to define the pattern.
Defining Delimiters
The first step is to define the delimiters, which are just forward slashes:
Defining the Start and End of the Pattern
Now we define the start and end of the pattern using ^ for the start and $ for the end:
Minimum of 8 Characters
The first condition for the password is that it must have at least 8 characters:
We have added .{8,}
The dot means any character.
{8,} means at least 8 characters and no maximum.
If we wanted to specify that the password must be exactly 8 characters then we would use .{8}
If we wanted to specify a minimum of 8 characters and a maximum of 20 characters for the password then we would use .{8,20}
Minimum of 1 Uppercase Character
Next, we need to have a minimum of 1 uppercase character:
We have added (?=.*[A-Z])
?= means look ahead through the password.
.* means look for any number of characters.
[A-Z] means look for any uppercase characters between A and Z inclusive.
Note that we have placed this part of the pattern BEFORE the minimum number check.
Minimum of 1 Number (Digit)
We have added (?=.*[0-9])
?= means look ahead through the password.
.* means look for any number of characters.
[0-9] means look for any digit between 0 and 9 inclusive.
Minimum of 1 of the Following Special Characters !@#$%^&*-
At this point you can probably guess what you need to include.
We have added (?=.*[!@#$%^&*-])
?= means look ahead through the password.
.* means look for any number of characters.
[!@#$%^&*-] means look for any of these characters.
