What are the string functions in php

php’s string functions are: 1. addcslashes(), returns a string with a backslash added before the specified character; 2. addslashes(), returns a character with a backslash added before the predefined character String; 3. bin2hex(), converts a string of ASCII characters into a hexadecimal value; 4. explode(), converts a string to an array; 5. implode(), converts an array to a string; 6. strcmp(), compares two strings; 7. strrev(), reverses a string.

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

String is one of the important data types in PHP one. In web development, string processing and analysis are required in many cases, which usually involves a series of operations such as string formatting, string concatenation and segmentation, string comparison, and search. The interaction between the user and the system is basically carried out using text, so the system's processing of text information, that is, strings, is very important.

PHP provides a large number of built-in functions for processing strings. Using these functions, you can easily complete various operations on strings in PHP programs.

Function	Description
addcslashes()	Returns adding a backslash before the specified character bar string.
addslashes()	Returns a string with backslashes added before predefined characters.
bin2hex()	Convert a string of ASCII characters to a hexadecimal value.
chop()	Remove whitespace characters or other characters on the right side of the string.
chr()	Returns characters from the specified ASCII value.
chunk_split()	Split the string into a series of smaller parts.
convert_cyr_string()	Convert a string from one Cyrillic character set to another.
convert_uudecode()	Decode the uuencode encoded string.
convert_uuencode()	Encode a string using the uuencode algorithm.
count_chars()	Returns information about the characters used in the string.
crc32()	Calculate the 32-bit CRC (Cyclic Redundancy Check) of a string.
crypt()	One-way string encryption (hashing).
echo()	Output one or more strings.
explode()	Break up the string into an array.
fprintf()	Write the formatted string to the specified output stream.
get_html_translation_table()	Returns the translation table used by htmlspecialchars() and htmlentities().
hebrev()	Convert Hebrew text to visible text.
hebrevc()	Convert Hebrew text to visible text, and convert new lines (\n) to .
hex2bin()	Convert a string of hexadecimal values ​​to ASCII characters.
html_entity_decode()	Convert HTML entities to characters.
htmlentities()	Convert characters into HTML entities.
htmlspecialchars_decode()	Convert some predefined HTML entities into characters.
htmlspecialchars()	Convert some predefined characters into HTML entities.
implode()	Returns a string composed of array elements.
join()	An alias for implode().
lcfirst()	Convert the first character in the string to lowercase.
levenshtein()	Returns the Levenshtein distance between two strings.
localeconv()	Returns local number and currency format information.
ltrim()	Remove whitespace characters or other characters on the left side of the string.
md5()	Computes the MD5 hash of a string.
md5_file()	Calculate the MD5 hash of the file.
metaphone()	Calculate the metaphone key of a string.
money_format()	Returns a string formatted as a currency string.
nl_langinfo()	Return the specified local information.
nl2br()	Inserts an HTML newline character before each new line in the string.
number_format()	Format a number by thousands grouping.
ord()	Returns the ASCII value of the first character in the string.
parse_str()	Parse the query string into variables.
print()	Output one or more strings.
printf()	Output formatted string.
quoted_printable_decode()	Convert quoted-printable string to 8-bit string.
quoted_printable_encode()	Convert 8-bit string to quoted-printable string.
quotemeta()	Quote metacharacters.
rtrim()	Remove whitespace characters or other characters on the right side of the string.
setlocale()	Set regional information (regional information).
sha1()	Computes the SHA-1 hash of a string.
sha1_file()	Compute the SHA-1 hash of a file.
similar_text()	Calculate the similarity of two strings.
soundex()	Calculate the soundex key of a string.
sprintf()	Write the formatted string into a variable.
sscanf()	Parses input from a string according to the specified format.
str_getcsv()	Parse the CSV string into an array.
str_ireplace()	Replace some characters in the string (case insensitive).
str_pad()	Padding the string to the new length.
str_repeat()	Repeat the string the specified number of times.
str_replace()	Replace some characters in the string (case sensitive).
str_rot13()	Perform ROT13 encoding on a string.
str_shuffle()	Randomly shuffles all characters in the string.
str_split()	Split the string into an array.
str_word_count()	Count the number of words in a string.
strcasecmp()	Compares two strings (case insensitive).
strchr()	Find the first occurrence of a string in another string. (Alias ​​for strstr().)
strcmp()	Compares two strings (case sensitive).
strcoll()	Compares two strings (according to local settings).
strcspn()	Returns the number of characters searched in a string before any specified character is found.
strip_tags()	Strip HTML and PHP tags from strings.
stripcslashes()	Remove backslashes added by the addcslashes() function.
stripslashes()	Remove backslashes added by addslashes() function.
stripos()	Returns the position of the first occurrence of a string in another string (case insensitive).
stristr()	Find the first occurrence of a string in another string (case insensitive).
strlen()	Returns the length of the string. Chinese string processing uses the mb_strlen() function.
strnatcasecmp()	Uses a "natural ordering" algorithm to compare two strings (case insensitive).
strnatcmp()	Uses a "natural ordering" algorithm to compare two strings (case sensitive).
strncasecmp()	String comparison of the first n characters (case insensitive).
strncmp()	String comparison of the first n characters (case sensitive).
strpbrk()	Search for any one of the specified characters in the string.
strpos()	Returns the position of the first occurrence of a string in another string (case sensitive).
strrchr()	Find the last occurrence of a string in another string.
strrev()	Reverse a string.
strripos()	Find the last occurrence of a string in another string (case insensitive).
strrpos()	Find the last occurrence of a string in another string (case sensitive).
strspn()	Returns the number of specific characters contained in a string.
strstr()	Find the first occurrence of a string in another string (case sensitive).
strtok()	Split the string into smaller strings.
strtolower()	Convert the string to lowercase letters.
strtoupper()	Convert the string to uppercase letters.
strtr()	Convert specific characters in the string.
substr()	Returns a part of the string.
mb_substr()	Returns part of the Chinese string.
substr_compare()	Compares two strings starting at the specified starting position (binary safe and selective case sensitive).
substr_count()	Count the number of times a substring appears in a string.
substr_replace()	Replace part of a string with another string.
trim()	Remove whitespace characters and other characters on both sides of the string.
ucfirst()	Convert the first character in the string to uppercase.
ucwords()	Convert the first character of each word in the string to uppercase.
vfprintf()	Write the formatted string to the specified output stream.
vprintf()	Output formatted string.
vsprintf()	Write the formatted string into the variable.
wordwrap()	Wraps the string according to the specified length.

String formatting

1. String truncation:

• trim ():

  Delete the characters (carriage return, line feed, tab) at the beginning and end of the string, and return the result string

  At the same time, the trim() parameter can also be set to a custom value Special character filter list

• rtrim():

  Delete special characters starting from the beginning of the string

• ltrim() :

  Delete special characters starting from the end of the string

• chop():

  Similar to the rtrim() function

2. Formatted output:

• htmlspecialchars(): function filters output

  htmlspecialchars(): function will Output a string as an HTML entity (characters with special meanings in the string can be translated into HTML entities)

• str_replace(): Regular filter output

• nl2br():HTML formatting

  nl2br(): The function takes a string as input and replaces the \n symbol in the string with the tag in HTML; this Useful for displaying a long string in an HTML browser.

• Character formatted output: sprintf()/printf()

  In character formatted output, use the % character format output control character to normalize characters

String case

• ##strtoupper(): String case

• strtolower(): String lowercase

• ucfirst(): Capitalize the first letter

• ucwords(): Change The first character of each English paragraph is capitalized

##String concatenation and segmentation

##explode( ): Based on the specified character as the split condition, return to an array

• strtok(): Decompose the string into a set of strings
• The separator can be one character It can also be a string. The strtok() function will only read out one substring each time based on the delimiter;
  substr():
• returns one character A new string result composed of the return of the given starting point and end point in the string
  string substr(string string, int start [,int length]);
• Function Return the string content in the string string according to the start and length constraints

String comparison

1. Sorting:

strcmp(): Compare two strings

• strcasecmp(): Compare strings (do not distinguish Upper and lower case)

• strnatcmp(): Natural sorting (not case sensitive)

• strlen(): Determine the string length
2. Character matching

1) String search:

strstr(): Match search characters Or string

• ##strchr(): Match and find a character

• ##strstr() and strchr() have no difference in matching and search applications. The function requires more than two parameters. The first parameter is: the string that needs to be searched, and the second parameter is: the target keyword to be searched; matching the string to the keyword will return the searched character. string, otherwise return false

• 2) String position:

strpos(): Returns the position of the matching character

• strpos(): The parameters of the function are similar to strstr(). The third parameter of strpos() can specify the position to start searching

• 3) String Replacement:

str_replace(): String replaces other characters in the string.

• Recommended learning: "

  PHP Video Tutorial

  "

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