PHP regular expression in practice: matching zip codes

PHP is a very powerful programming language that can be used to create dynamic web pages. In PHP programming, regular expressions are an important part. Regular expressions are a language used to describe text patterns and can be used for matching, searching, replacing, filtering and other operations. This article will explain how to use PHP regular expressions to actually match zip codes.

Postal code is a numerical code that identifies a postal area and is used to speed up the delivery of mail and improve its accuracy. In China, the postal code consists of 6 digits, such as: 100000, 200000, 300000, etc. Below we will use PHP regular expressions to match these zip codes.

First, we need to understand the syntax of regular expressions. Regular expressions consist of a series of characters and special characters, where special characters are used to express some specific meanings. Here are some commonly used regular expression special characters:

• ^: Matches the beginning of a string.
• $: Matches the end of the string.
• .: Matches any character.
• *: Matches the previous character 0 or more times.
• : Matches the previous character 1 or more times.
• ?: Match the previous character 0 or 1 times.
• []: Matches any character within square brackets.
• {}: Limit the number of repetitions. For example, {2,5} means matching 2 to 5 times.

Next, we will build a regular expression using the above special characters to match zip codes.

First, we need to match 6 digits. You can use the d special character to match any number. {6} is limited to 6 matches, and a regular expression of d{6} can be constructed. This regular expression can match any 6-digit number. But if we want to match only China’s postal codes (that is, the starting numbers can only be 1, 2, 3), we can pass ^1[0-9]{5}$, ^2[0-9]{5}$, ^3[0-9]{5}$ Three regular expressions are completed. Among them, ^1[0-9]{5}$ means starting with the number 1, followed by 5 numbers, and finally ending with a string; similarly, ^2[0-9]{5}$ means starting with the number 2 , ^3[0-9]{5}$ means starting with the number 3.

Next, we need to use regular expressions in the PHP code to verify whether the zip code matches. The following is a piece of code that uses the preg_match function to verify the zip code:

<?php
$zip_code = "100000";
$pattern = "/^1[0-9]{5}$|^2[0-9]{5}$|^3[0-9]{5}$/";
if (preg_match($pattern, $zip_code))
{
  echo "该邮编是中国的邮编。";
}
else
{
  echo "该邮编不是中国的邮编。";
}
?>

In the above code, $zip_code stores the zip code to be verified. $pattern stores the regular expression used to match 6-digit numbers. The preg_match function matches zip codes with regular expressions. If the match is successful, it means that the postal code is a Chinese postal code, otherwise it is a non-Chinese postal code.

The above is the entire content of using PHP regular expressions to actually match zip codes. Readers can try to use regular expressions to match other types of text according to their own needs.

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