A brief analysis of regular expressions for checking email_PHP tutorial

What method do we need to use to implement the regular expression for checking email? What are the steps required to check the regular expression of email? The operation example of checking the regular expression of email will be shown to you in detail.

Let's move on to how to verify an email address. There are three parts in a complete email address: POP3 username (everything to the left of '@'), '@', servername (that's the rest that part). Usernames can contain uppercase and lowercase letters, Arabic numerals, periods ('.'), minus signs ('-'), and underscores ('_'). Server names also comply with this rule, except of course underscores.

Related discussion of regular expressions for checking email:

Now, usernames cannot start and end with periods. The same goes for servers. Also you can’t have two There must be at least one character between consecutive periods. Now let’s take a look at how to write a matching pattern for the username:

^[_a-zA-Z0-9-]+$

The existence of periods is not allowed yet. We add it:

^[_a-zA-Z0-9-]+(.[_a-zA-Z0-9-]+)*$

The above means: "Start with at least one standard character (except . and unexpected), followed by 0 or more strings starting with a dot."

Check email Implementation of regular expression:

To simplify it a bit, we can use eregi() instead of ereg(). eregi() is not case-sensitive, so we don’t need to specify the two ranges "a-z " and "A-Z" – just specify one:

^[_a-z0-9-]+(.[_a-z0-9-]+)*$

The following server name is the same, but the underscore must be removed:

^[a-z0-9-]+(.[a-z0-9-]+)*$

Done. Now you just need to use "@" to connect the two parts:

^[_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-] +(.[a-z0-9-]+)*$

This is the complete email authentication matching mode. You only need to call

eregi('^[_a-z0-9 -]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*$ ',$eamil)

You can get whether it is email.

This concludes the introduction to you about regular expressions for checking emails. I hope it will be helpful for you to understand and learn the operation of regular expressions for checking emails.

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