1, splicing strings
Splicing strings is the most commonly used character One of the string operations, PHP supports three ways to splice strings, namely dot.separator {} operation, and dot equal sign.= to perform operations. The dot equal sign can compare a It is more beneficial to break a long string into several lines for definition.
2. Replacement string
In the PHP language, a name is provided The function called substr_replace() can quickly complete the scanning and editing of string replacement functions with large text content. Its syntax format:
mixed substr_replace(mixed $string, string $replacement, int $start[,int $length])
Explanation of the above syntax format:
string is the string to be checked or to be replaced
replacement specifies the String used to insert or replace
start specifies where in the string to start replacing. This parameter can take three types of values (positive number: start offset from the beginning of the string Start replacement, negative number, start replacing from the start offset at the end of the string, 0: start replacing from the first character in the string)
length specifies how many characters to replace, this parameter It can also take three types of values (positive number: the length of the string to be replaced, negative number: the length of the string to be replaced starting from the end of the string, 0: it is an insertion operation, not a replacement operation);
3, Calculate the string
1) Calculate the length of the string
In PHP, the strlen() function is used to calculate the length of the string and Returns 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.
2) Calculate the string The number of
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 format of the substr_count() function 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 is used 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 It is very convenient and accurate to determine how many words there are in the provided string. The syntax format of 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, and format is used to specify the return value of the str_word_count() function. The return value of this parameter can return three values, respectively. It is 0, 1, 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 key names are consecutive starting from 0. Integer, the value is the actual word. 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. Search string
Searching for strings 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.
1) Find substrings
In PHP language, the strstr() function can be used to find substrings String, the result returned by this function is all the content 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 The description is as follows: haystack: specifies the string to be searched, and needle specifies the string to be searched. If the parameter is a number, it will match the character of the ASCII value of the number. In actual applications, the letter size will be ignored. In the case of writing, at this time, you can use the stristr() function, a case-insensitive search function provided by PHP. The use of this function is the same as the strstr() function.
2 ) Find the position of the 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. The syntax format of strpos() 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, needle specifies the string to be searched, and offset is Specify the position to start searching. The default value is 0.
The strpos() function is a case-sensitive search function. However, in actual application processes, it is often necessary to ignore case. In this case, you can Use stripos(), a case-insensitive search function provided by PHP. 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
1) Using "==" Operators compare the size of two strings
When comparing two strings in PHP, the easiest way is to use the double equal sign operator (==).
2) Use functions to compare the sizes 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) as mentioned above The parameters involved in the syntax are described as follows: str1 specifies the string 1 to be compared, str2 specifies the string 2 to be compared. This strcmp function can ensure whether the two strings completely match, and the comparison result will be an integer. Return form, 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, then It means that the previous string is larger than the following string.
In addition to the strcmp() function, PHP also provides some other similar comparison functions. For example, the strncmp() function can choose what you want. The length (number of characters) of the compared strings, the syntax format is as follows: int strcmp (string $str1, string $str2, int $len) The above parameter description str1: specifies the first string to be compared, str2: Specify the second string len to be compared: specify the number of characters used for comparison in each string.
When comparing strings, sometimes you need to ignore case, you can use strcasemp( ) function and strncasemp() function, these two functions are used in exactly the same way as the corresponding case-sensitive functions. The syntax formats of the strcasecmp() function and strncasecmp() function 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 , flipping strings
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 dealing with string operations. Use the explode() function, str_split() function, and implode() function provided by PHP to handle problems like splitting and merging strings.
1) Split strings 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]) In the above syntax The parameters involved are explained 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, and the final sub-block will contain the remainder of the string. Part.
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]) In the above syntax The parameter description is as follows: string: specifies the string to be split, split_length: specifies the length of each array element, the default value is "1".
2) Merge strings
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). The parameters involved in the above syntax are described as follows: glue() specifies the content placed between 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 character according to the conditions restricted by the parameters. string 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 print characters String formatting operation
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 into "
" in HTML and display it.
4)wordwrap( ) function: Specify forced line breaks 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 the 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 All characters are converted to uppercase characters
8) substr_replace() function: can quickly scan and edit strings with large text content
9) strlen() function: can count characters The length of the string and returns 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 , you 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 the number of occurrences after the first occurrence of the substring. All content
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 of the string to be compared ( Number of characters)
16) The strcasecmp() function can compare two strings while ignoring case
17) The strncasecmp() function can ignore case Under the premise, compare the length or number of characters between two strings.
18) str_repeat() function, the function of displaying a character or string repeatedly n times
19) The strrev() function provides the operation of flipping a string
20) The explode() function provides the function of splitting a string into multiple strings. Specify the delimiter to split the string. Divide into arrays.
21) The str_split() function can split a string into multiple substrings of equal length
22) The implode() function connects the elements of the array into 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
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