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This article mainly introduces "how to split strings and escaped strings in PHP regular expressions". In daily operations, I believe many people have doubts about how to split strings and escaped strings in PHP regular expressions. Xiaobian consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "how to split strings and escaped strings in PHP regular expressions". Next, please follow the editor to study!

Preg_split () function

In PHP, the preg_split () function splits strings through a regular expression, and the syntax format of this function is as follows:

Array preg_split (string $pattern, string $subject [, int $limit =-1 [, int $flags = 0]])

Among them, it should be noted that:

$pattern represents the pattern used for matching, that is, the regular expression; $subject represents the string to be separated; $limit is an optional parameter, and if specified, the maximum number of substrings delimited is limit, and the last substring will contain all the rest. Limit values of-1, 0 or NULL all represent "unlimited" and it is recommended that you use NULL.

$flags is an optional parameter that has three values. If set to PREG_SPLIT_NO_EMPTY, preg_split () returns the delimited non-empty part. If set to PREG_SPLIT_DELIM_CAPTURE, parenthetical expressions in delimited patterns are captured and returned. If set to PREG_SPLIT_OFFSET_CAPTURE, a string offset is appended when each occurrence of the match is returned.

This changes each element in the returned array so that each element becomes an array of substrings separated by the 0th element, and the first element is the offset of the substring in the subject. The return value is an array of substrings obtained by splitting the subject string with pattern.

Next, let's take a look at the use of the preg_split () function through an example, as follows:

Output result:

Examples are as follows:

Output result:

As you can see from the above example, the preg_split () function can split a string through a real expression. Let's take a look at how to escape regular expressions.

PHP preg_quote () function

Normal characters include all printable and non-printable characters that are not explicitly specified as metacharacters, including all uppercase and lowercase letters, numbers, punctuation, and some symbols. The simplest regular expression is a single ordinary character used to compare a search string. For example, the single character regular expression / A / always matches the letter A.

In addition to ordinary characters, regular expressions can also contain metacharacters. Metacharacters can be divided into single-character metacharacters and multicharacter metacharacters. For example, the metacharacter\ d, which matches numeric characters.

The PHP preg_quote () function is used to escape the regular expression string by adding a backslash\ before the special character. The syntax format of this function is as follows:

Preg_quote ($str [, $delimiter = NULL])

Among them, it should be noted that:

Str represents a regular expression string; $delimiter is an optional parameter with additional characters that need to be escaped. If the $delimiter parameter is specified, the specified character is also escaped. This is typically used to escape the delimiter used by the PCRE function. / is the most common delimiter.

The preg_quote () function adds a backslash to the character of each regular expression provided by the argument $str. This is usually used when runtime strings need to be matched as regular expressions.

The special characters of regular expressions are:. \ + *? [^] $() {} =! |:- Be clear / not regular expression special characters.

Next, let's take a look at escaping a string using the preg_quote () function through an example, as follows:

Output result:

Examples are as follows:

Output result:

In the above example, the regular expression string is escaped through the preg_quote () function.

At this point, the study on "how to split strings and escaped strings in PHP regular expressions" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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