Summary of common string processing in PHP development_PHP tutorial

In the process of programming, string operations are very important and often used. Common string operations include string splicing, string replacement, string search, and character comparison. Strings, copy strings and calculate the length of strings, etc.

1. Concatenate strings

Splicing strings is one of the most commonly used string operations. PHP supports three ways to splice strings, namely the dot.separator{} operation and the dot equal sign. = to operate, the dot equal sign can break a relatively long string into several lines for definition, which is more beneficial.

2. Replace string

In the PHP language, a function called substr_replace() is provided. The function of this function can quickly complete the scanning and editing of string replacement functions with large text content. His syntax format: mixed substr_replace(mixed $string,string $replacement,int $start,[int $length])

3. Compute string

Calculate the length of a string: In PHP, the strlen() function is used to calculate the length of a string and return the length information of the string. The format of this syntax is as follows: int strlen(string $string) The string in the format is used to specify the string whose length is to be calculated.

Count the number of strings: In PHP, the substr_count() function can be used to very conveniently and accurately determine how many specified substrings there are in the provided string. The syntax of the substr_count() function The format is as follows: int substr_count(string $haystack,string $needle[,int $offset=0[,int $length]]) The description of the parameters designed in the above syntax is as follows: haystack specifies the string to be checked, and needle uses To specify the string to be inserted, offset is used to specify where to start searching in the string, the default value is 0, and length is used to specify the length of the search.

In PHP, the str_word_count() function can be used to very conveniently and accurately determine how many words there are in the provided string. The syntax format of the str_word_count() function is as follows: mixed str_word_count(string $ string[,int $format=0[,string $charlist]]) The description of the parameters involved in the above syntax is as follows: string is used to specify the string to be checked, format is used to specify the return of the str_word_count() function Value, the return value of this parameter can return three values, namely 0, 1, and 2. Returning 0 means the default value, which returns the number of words found. If the return value is 1, then str_word_count() returns an array in which the keys are consecutive integers starting from 0 and the values ​​are the actual words. . If the value of format is 3, then the return value of the str_word_count() function is an array, where the key of the array is the position of the word in the string, and the value is the actual word.

4. Find string

String search can be divided into many types, such as finding substrings, finding the position of a certain string, etc. PHP provides corresponding functions for each string search operation.

Finding substrings: In PHP language, the strstr() function can be used to find substrings. The result returned by this function is all the contents of the first occurrence of the substring. The format of the strstr() function is as follows : string strstr(string $haystack, mixed $needle) In the above syntax, the parameters involved are explained as follows haystack: specifies the string to be searched, and needle specifies the string to be searched. If the parameter is a number, then Characters that will match the ASCII value of the number. In actual applications, there may be situations where the case of letters needs to be ignored. In this case, you can use the strstr() function, a case-insensitive search function provided by PHP. The usage of this function is the same as that of the strstr() function. The usage is the same.

Find the position of a string: The function of the strpos() function is similar to the strstr() function, except that it returns not a string, but the position where a string first appears in another string, strpos The syntax format of () is as follows: int strpos(string $haystack, mixed $needle[,int $offset =0]) The parameters involved in the above syntax are explained as follows: haystack is the string to be searched, and needle is specified The string to be searched, offset specifies the position to start searching, and the default value is 0.

The strpos() function is a case-sensitive search function. However, in actual applications, it is often necessary to ignore case. In this case, you can use a search function provided by PHP that is not very case-sensitive. stripos(), the usage of this function is the same as strpos().

5. Compare strings

In PHP language, comparing the size of two strings can be achieved in two ways: using the "==" operator to compare and using functions to compare

Use the "==" operator to compare the sizes of two strings: When comparing two strings in PHP, the easiest way is to use the double equal sign operator (==).

Use functions to compare the size of strings: The strcmp() function provided in PHP can more accurately compare the sizes of two strings. The syntax format is as follows int strcmp(string $str1, string $str2) In the above syntax The description of the parameters involved is as follows: str1 specifies the string 1 to be compared, and str2 specifies the string 2 to be compared. This strcmp function can ensure whether the two strings completely match and return the comparison result in the form of an integer. The return value of this function has the following three types. 0: The two strings are equal. When it is less than 0, the first string is smaller than the following string. If the return value is greater than zero, it means that the previous string is larger than the following string. of.

In addition to the strcmp() function, PHP also provides some other similar comparison functions. For example, the strncmp() function can select the length (number of characters) of the string you want to compare. Its syntax format is as follows: int strcmp (string $str1, string $str2, int $len) Parameter description above str1: Specify the first string to be compared, str2: Specify the second string to be compared len: Specify each string for The number of characters to compare.

When comparing strings, sometimes you need to ignore case, so you can use the strcasemp() function and strncasemp() function. The usage of these two functions is exactly the same as the corresponding case-sensitive functions. The syntax formats of the strcasecmp() function and strncasecmp() are as follows:

int strcasecmp(string $str1,string $str2)

int strncasecmp(string $str1,string $str2,int $len)

6. Copy string

If you need to display a character or a string repeatedly n times, the simplest way to implement it is to call the copy function. In PHP, you can use the str_repeat() function to copy the string. The syntax format of this function is as follows : string str_repeat(string $input, int $multiplier) The description of the parameters designed in the above syntax is as follows: input specifies the string to be repeated, and multiplier specifies the number of times the string will be repeated.

7. Flip the string

The operation of processing strings also includes flipping strings. In PHP language, the function of reversing strings can be realized by using the strrev() function. The syntax format of the strrev() function is: string strrev(string $string)

The above parameter string is used to specify the string to be flipped.

8. Split and merge strings

Splitting a string into multiple strings according to certain rules, or merging multiple strings into one long string, is a problem that is often encountered when processing string operations. Use the explode() function, str_split() function, and implode() function provided by PHP to handle problems like splitting and merging strings.

Split string: The function of the explode() function is to split the string into an array using the specified delimiter. The syntax format of the explode() function is as follows: array explode(string $delimiter,string $string[,int $ limit]) The description of the parameters involved in the above syntax is as follows: delimiter: specifies where to separate the string, string: specifies the string to be split, limit: specifies the maximum number of array elements returned, the last sub The block will contain the remainder of the string.

The function of str_split() function is to split a string into multiple substrings of equal length. The syntax format of str_split() function is as follows: array str_split(string $string[,int $split_length=1]) The parameters in the above syntax are as follows: string: specifies the string to be split, split_length: specifies the length of each array element Length, default value is "1".

Combine strings: The function of the implode() function is to connect the elements of the array into a string. The syntax format of the implode() function is as follows: string implode([string $glue],array $pieces) In the above syntax The description of the parameters involved is as follows: glue() specifies the content placed between the array elements. The default value is "" (representing a space string) pieces specifies the array to be merged into a string. Calling the implode() function can obtain a new string according to the conditions restricted by the parameters to achieve the purpose of merging strings.

join() is an alias of the implode() function. The usage of the two functions is exactly the same. It needs to be emphasized that although the parameter glue is optional, in order to make the program have better compatibility, it is recommended to use Two parameters.

Summarize the related operation methods of strings:

1. printf() function: can perform formatting operations on strings
2. sprintf() function: You can format a string. The difference from the printf() function is that you need to use echo to display and output the formatted string.
3. nl2br() function: You can convert the newline character "n" in the string to "
   " in HTML and display it.
4. Wordwrap() function: Specify forced line wrapping from a certain column of characters
5. strtolower() function: The function implemented by this function is to convert all characters in the string into lowercase characters
6. strtoupper() function: The function of this function is to convert all characters in the string into uppercase characters
7. ucwords() function: The function of this function is to convert all the first characters in the string into uppercase characters
8. substr_replace() function: a function that can quickly scan and edit strings with large text content
9. strlen() function: can calculate the length of a string and return the length of the string
10. substr_count() function: You can determine how many strings there are in the provided string
11. str_word_count() function can determine the number of occurrences of a certain word in a string.
12. The strstr() function can be used to find substrings. The return result of this function is all the content after the first occurrence of the substring
13. The strpos() function is similar to the strstr() function, except that it returns not a string, but the position of the first occurrence of one string in another string.
14. strcmp() function, this function can accurately compare the size of two strings
15. strncmp() function, you can choose the length (number of characters) of the string to be compared
16. The strcasecmp() function can compare two strings while ignoring case
17. The strncasecmp() function can compare the length or number of characters of two strings while ignoring case.
18. str_repeat() function, the function of displaying a character or string repeatedly n times
19. strrev() function provides the operation of flipping strings
20. The explode() function provides the function of splitting a string into multiple strings. Specify the separator to split the string into an array.
21. The str_split() function can split a string into multiple substrings of equal length
22. implode() function, concatenates the elements of the array into a string
23. The join() function is used exactly the same as the implode() function. Its function is also to connect the array elements into a string

http://www.bkjia.com/PHPjc/752384.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/752384.htmlTechArticleIn the process of programming, string operations are very important and often used. Strings are commonly used Specific operations include string splicing, string replacement, and string search...