Regular expressions for verifying email address can be implemented through regex in PHP. The common writing method is: ^[a-zA-Z0-9.\_% -] @[a-zA-Z0-9.-] \.[a-zA-Z]{2,}$. 1. The user name part allows letters, numbers and partial symbols, such as dots, underscores, percent signs, etc., to represent at least one character; 2. The domain name part consists of letters, numbers, dots and minus signs, and the top-level domain name requires more than two letters; 3. This rule is suitable for most actual scenarios, but does not fully comply with the RFC standard; 4. It is recommended to use the PHP built-in function filter_var() for verification first; 5. When using the rule, you can consider adding modifiers i and u to improve compatibility.
Regular expressions for verifying email addresses are a common requirement in PHP. Although PHP has a built-in function filter_var() that can be used directly to verify mailboxes, sometimes you may need more flexible control, and you need to use regular expressions (regex).
The following regular expression is a relatively general way to write it in terms of practicality and compatibility:
$email = "example@test.com";
if (preg_match("/^[a-zA-Z0-9._% -] @[a-zA-Z0-9.-] \.[a-zA-Z]{2,}$/", $email)) {
echo "valid mailbox";
} else {
echo "Invalid mailbox";
}The structure of this regular expression can be broken down into several parts to understand.
Email username part: [a-zA-Z0-9._% -]
The @ of the mailbox is preceded by the username part, which usually allows the following characters:
- Letters az and AZ
- Numbers 0-9
- dot number
., underline__percent sign%, plus sign-
Note that this is used here Indicates that there is at least one character.
Common legal user names such as:
- john.doe
- user 123
- test%email
So this part of regular writing: [a-zA-Z0-9._% -]
Email domain name part: [a-zA-Z0-9.-] \.[a-zA-Z]{2,}
@The following part is domain names and top-level domain names, such as gmail.com or mail.co.uk
- The domain name body consists of letters, numbers, dots and minus signs:
[a-zA-Z0-9.-] - Then there is a dot number
\.(Please escape) - Finally, there are top-level domains, usually two or more letters:
[a-zA-Z]{2,}
For example:
- example.com ?
- sub.mail.co.uk ?
- exa_mple.com ? (Domain name does not allow underscore)
Some things to note
- This regularity is loose and will not cover all legal mailbox formats defined by RFC standards, but can meet most practical usage scenarios.
- If you pursue extreme standard compatibility, the rules will become very complex, even hundreds of characters, but they are not recommended in daily development.
- Users are not advised to build their own wheels unless there are special needs. PHP's
filter_var($email, FILTER_VALIDATE_EMAIL)is a safer choice.
Tips: Common modifiers for PHP regular
If you have problems using regulars, check if the modifier is missing:
-
i: case insensitive (optional) -
u: Process UTF-8 encoding (if international mailbox is supported, you can add it)
For example:
"/^[a-zA-Z0-9._% -] @[a-zA-Z0-9.-] \.[a-zA-Z]{2,}$/iu"Basically that's it. If you use this rule well, you can complete the basic verification of the email format in most cases.
The above is the detailed content of php regex for email validation. For more information, please follow other related articles on the PHP Chinese website!
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