How to use PHP7.0 for regular expression matching?

With the development of Internet technology, PHP, as a popular programming language, has been widely used in Web development. Regular expressions are also one of the commonly used tools in web development for matching strings and text. PHP version 7.0 and above provide powerful support for regular expressions. This article explains how to use PHP 7.0 for regular expression matching.

1. Basic syntax of regular expressions

Regular expression is a string matching pattern, consisting of some characters and special symbols. In PHP, you can use the preg_match() function for regular expression matching. The following is some basic syntax of regular expressions:

• Metacharacters

Metacharacters are special characters in regular expressions, used to represent some special matching rules. For example, the period (.) means matching any character, the asterisk (*) means matching zero or more characters, the plus sign ( ) means matching one or more characters, and the question mark (?) means matching zero or one character.

• Character set

The character set is enclosed in square brackets, which means matching any character in a character set. For example, the character set [abc] means match any of the characters a, b, or c.

• Escape characters

Some special characters need to be escaped before they can be used. For example, backslash () represents an escape character, and a left bracket (() represents the start of a capture group. , the right bracket ()) indicates the end of the capture group.

2. Usage of preg_match() function

In PHP, you can use the preg_match() function to match regular expressions. The basic syntax of this function is as follows:

preg_match(pattern, subject, matches, flags, offset);

Parameter description:

• pattern: regular expression pattern;
• subject: target string;
• matches (optional): array in which matching results are stored;
• flags (optional): matching flags, optional values ​​include: i, m, s and U;
• offset (optional) (optional): Search the offset of the starting position.

The following is an example of regular expression matching on a string:

$str = "Hello, world!";
if (preg_match("/Hello/", $str) === 1) {
    echo "匹配成功！";
} else {
    echo "匹配失败！";
}

The above code will output: Match successful!

3. Commonly used regular expression patterns

• Match numbers

preg_match("/^d+$/", $str);

• Match dates

preg_match("/^d{4}-d{2}-d{2}$/", $str);

• Match email address

preg_match("/^w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*$/", $str);

• Match URL

preg_match("/^(http|https)://[a-z0-9]+([-.]{1}[a-z0-9]+)*.[a-z]{2,5}(([0-9]{1,5})?/.*)?$/", $str);

• Match mobile phone number

preg_match("/^1[3456789]d{9}$/", $str);

4. Usage of preg_match_all() function

The preg_match_all() function is similar to the preg_match() function and is also used for regular expression matching. The difference is that it matches all occurrences in the target string and stores all matching results in an array instead of returning the first matching result. The basic

syntax of the function is as follows:

preg_match_all(pattern, subject, matches, flags, offset);

The parameter description is the same as the preg_match() function.

The following is an example:

$str = "https://www.example.com https://www.google.com https://www.facebook.com";
preg_match_all("/https://www.w+.com/", $str, $matches);
print_r($matches[0]);

The above code will output:

Array
(
    [0] => https://www.example.com
    [1] => https://www.google.com
    [2] => https://www.facebook.com
)

5. preg_replace() usage

preg_replace () function is used to replace regular expressions in the target string. The basic syntax of the function is as follows:

preg_replace(pattern, replacement, subject, limit, count);

Parameter description:

• pattern: regular expression pattern;
• replacement: replacement string or callback function;
• subject: target string;
• limit (optional): the maximum number of substitutions;
• count (optional): a variable used to store the number of substitutions.

The following is an example:

$str = "Hello, world!";
echo preg_replace("/Hello/", "Hi", $str);

The above code will output: Hi, world!

In short, regular expressions are a very powerful tool. Very useful when doing string matching and replacement. PHP 7.0 provides powerful regular expression support, making using regular expressions in PHP very easy. We only need to learn the basic syntax and common patterns of regular expressions to easily match and replace strings.

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