Verifying regular expressions for phone numbers is not difficult in PHP, but the key is to clarify the format standards of legal phone numbers. 1. Different countries and business scenarios have different requirements for phone number formats, so general regularity is unrealistic; 2. Common formats include pure numbers, area codes, hyphens, international area code beginnings, extension numbers, etc.; 3. PHP uses the preg_match() function to perform regular matching, and rules can be flexibly written according to requirements; 4. When designing regularity, elements such as supporting digits, allowing symbols, whether international area codes are included; 5. Common errors include trying to cover all formats, ignoring boundary conditions, not conducting multi-case tests, and relying only on back-end verification. It is recommended to customize regular expressions according to specific project needs and do two-factor verification before and after.

Verifying regular expressions for phone numbers is actually not difficult in PHP, but the difficulty lies in the question of "what kind of phone number is legal" itself does not have a unified standard. The requirements for phone number formats in different countries and business scenarios may be completely different.

So, it is not realistic to write a common regularity to verify all phone numbers. A more practical approach is to customize the rules according to your specific needs.

What are the common phone number formats?

There are many ways to write a phone number, such as:

• Pure number: 1234567890
• Area Code: (123) 456-7890
• With hyphen: 123-456-7890
• Starting with international domain code: 1 123 456 7890
• Extended number: 123-456-7890 x12

These formats may exist, so before writing the rules, you have to think clearly which or several formats you want to accept.

How to use regular verification of phone numbers in PHP?

PHP uses the preg_match() function to match regular expressions. The following is a relatively flexible example, supporting formats such as brackets, spaces, hyphens, international prefixes, etc.:

 $pattern = '/^\ ?1?\s*$$?\d{3}$$?[\s\-]?\d{3}[\s\-]?\d{4}$/';
if (preg_match($pattern, $phone)) {
    echo "The phone number is in the correct format";
} else {
    echo "The phone number format is incorrect";
}

This regular explanation is as follows:

• ^ and $ represent exact match from beginning to end
• \ ?1? Optional international domain code (such as 1)
• \s* Match zero or more spaces
• $$?\d{3}$$? Supports three-digit area codes, can be bracketed
• [\s\-]? Optional space or hyphen
• Finally, the complete seven-digit number

You can adjust the length and allowable symbols according to your needs.

How to design a phone routine that suits your project?

We recommend that you consider the following aspects:

• How many digits do you need to support? (For example, 10-bit, 11-bit)
• Are spaces, hyphens, and brackets allowed?
• Are international domain codes allowed?
• Do I need to force some formats?

For example:

If you only accept Chinese mobile phone numbers (11 digits, starting with 13, 14, 15, 17, 18, 19), you can use this rule:

 $pattern = '/^1[345789]\d{9}$/';

If it is a US number (10 digits, maybe with area code), you can do this:

 $pattern = '/^$$?\d{3}$$?[\s\-]?\d{3}[\s\-]?\d{4}$/';

Common Errors and Precautions

• Don't try to overwrite all formats : the more general the regularity is, the more likely it is to make mistakes, and it's better to limit the user input format.
• Pay attention to boundary conditions : For example, no less or more ones should be passed.
• Test a variety of situations : including illegal characters, excessive spaces, confusing formats, etc.
• The front-end also needs to be verified : PHP is back-end verification, but it is best to check both the front-end and the back-end.

Basically that's it. The rules of the phone number are not fixed, the key is to customize the appropriate rules according to your project requirements.

The above is the detailed content of php regex to validate a phone number. For more information, please follow other related articles on the PHP Chinese website!