PHP string Common functions

arrays, strings, and databases are the most, most, and most commonly used functions in our functions, arrays and databases We haven't talked about it yet, and we'll come back to you when we talk about it.

Of course, there are many string functions in PHP. The two series of strings we use most often:

1. Single byte string processing function

2. Multibyte string processing functions

3. String encoding conversion function

Let's say why we need to learn so many functions:

1. We are learning Chinese, which is double-byte or three-byte. The foreigner's function can only handle English and the number of these single-byte string processing does not bird Chinese. Not up to our functional requirements

2. Sometimes it is necessary to do the conversion between different character encodings, for example: converting GBK to UTF-8

3. English these characters must be dealt with in the computer.

PHP Common functions

The main use of Chinese is GBK and utf-8 two encoding format.
GBK and Utf-8 are two different coding boards that encode the Chinese characters.

They stipulate that GBK is double-byte, that is, a Chinese character occupies 2Bytes.
The Utf-8 is three bytes, and a Chinese character occupies three bytes of storage space.

Name of function	Description	Example
Trim ()	Remove spaces or other predefined characters at each end of a string	"$str =" \r\nhello world!\r\n "; echo Trim ($STR);
RTrim ()	Remove whitespace or other predefined characters to the right of a string	"$str =" Hello world!\n\n "; echo RTrim ($STR); "
Chop ()	Alias for RTrim ()	Ditto
LTrim ()	Remove spaces or other predefined characters to the left of a string	"$str =" \r\nhello world! "; Echo LTrim ($STR); "
DirName ()	Back to the directory part of the path (we put it in the string function)	Echo dirname ("c:/testweb/home.php");
Str_pad ()	Fills a string with the specified length	$STR = "Hello World"; Echo Str_pad ($str, 20, ".");
Str_repeat ()	Reusing the specified string	Echo str_repeat (".", 13);
Str_split ()	To split a string into an array	Print_r (Str_split ("Hello"));
Strrev ()	Invert string	Echo Strrev ("Hello world!");
WordWrap ()	Wrapping a string by a specified length	"$STR =" "An example on a long word is:supercalifragulistic" "; Echo WordWrap ($STR, 15); "
Str_shuffle ()	Randomly disrupts all characters in a string	Echo str_shuffle ("Hello World");
Parse_str ()	Parsing a string into a variable	"Parse_str (" Id=23&name=john%20adams ", $myArray); Print_r ($myArray); "
Number_format ()	Formatting numbers with thousands of groupings	"Echo Number_format (" 1000000 "); Echo Number_format ("1000000", 2); Echo Number_format ("1000000", 2, "", "", "". ");"
Strtolower ()	String converted to lowercase	Echo strtolower ("Hello world!");
Strtoupper ()	String to uppercase	Echo strtoupper ("Hello world!");
Ucfirst ()	Capitalize the first letter of the string	echo ucfirst ("Hello World");
Ucwords ()	String each word first character to uppercase	echo ucwords ("Hello World");
Htmlentities ()	Convert a character to an HTML entity	$str = "John & ' Adams '"; Echo htmlentities ($str, Ent_compat);
Htmlspecialchars ()	Predefined word representable HTML encoding
NL2BR ()	\ n escaped as Label	Echo nl2br ("One line.\nanother line.");
Strip_tags ()	Strip HTML, XML, and PHP tags	Echo strip_tags ("Hello world!");
Addcslashes ()	Adds a backslash to an escaped character in a string before the specified character	$str = "" Hello, my name is John Adams. "Echo $str; Echo addcslashes ($str, ' m '); "
Stripcslashes ()	Remove the backslash added by Addcslashes ()	Echo stripcslashes ("Hello, \my Na\me is Kai ji\m.");
Addslashes ()	To add a backslash before specifying a predefined character	$str = "Who ' s John Adams?"; echo addslashes ($STR);
Stripslashes ()	Remove the escape character added by Addslashes ()	Echo stripslashes ("who\ ' s John Adams?");
Quotemeta ()	Add a backslash before certain predefined characters in the string	$STR = "Hello World". (Can you hear me?) "; echo Quotemeta ($STR);
Chr ()	Returns the character from the specified ASCII value	Echo Chr (052);
Ord ()	Returns the ASCII value of the first character of a string	echo ord ("Hello");
STRCASECMP ()	Case-insensitive comparison of two strings	echo strcasecmp ("Hello world!", "Hello world!");
strcmp ()	Case-sensitive comparison of two strings
STRNCMP ()	Compares the first n characters of a string, case sensitive
STRNCASECMP ()	Compares the first n characters of a string, not case-sensitive	int strncasecmp (String $str 1, String $str 2, int $len)
STRNATCMP ()	Natural order method compares string length, case sensitive	int strnatcmp (String $str 1, String $str 2)
STRNATCASECMP ()	Natural order method compares string length, case-insensitive	int strnatcasecmp (String $str 1, String $str 2)
Chunk_split ()	Divide a string into small chunks	Str chunk_split (str $body [, int $len [, str $end]]
Strtok ()	Cut string	Str strtok (str $str, str $token)
Explode ()	Use one string to split another string for a flag	Array explode (str $sep, str $str [, int $limit])
Implode ()	Join, concatenate the array values with the subscription character into a string	String implode (string $glue, array $pieces)
SUBSTR ()	Intercept string	String substr (string $string, int $start [, int $length])
Str_replace ()	String substitution operations, case-sensitive	Mix str_replace (Mix $search, Mix $replace, Mix $subject [, int & $num])
Str_ireplace ()	String substitution operation, case insensitive	Mix str_ireplace (Mix $search, Mix $replace, Mix $subject [, int & $count])
Substr_count ()	Counts the number of occurrences of a string in another string	int Substr_count (string $haystack, string $needle [, int $offset = 0 [, int $length]])
Substr_replace ()	Replace a string in another string	Mixed Substr_replace (mixed $string, string $replacement, int $start [, int $length])
Similar_text ()	Returns the number of identical characters in two strings	int Similar_text (str $str 1,str $str 2)
STRCHR ()	Returns a string in another string starting at the end of a string	String Strstr (String $str, String $needle, bool $before _needle)
STRRCHR ()	Returns a string in another string where the last occurrence of the position begins at the end of the string	String STRRCHR (String $haystack, mixed $needle)
Stristr ()	Returns a string in another string starting at the end of the string, not case-sensitive	String Stristr (String $haystack, mixed $needle [, bool $before _needle = false])
STRTR ()	Convert some characters in a string	String Strtr (String $str, String $from, String $to)
Strpos ()	Finding where a character in a string first appears	int Strpos (string $haystack, mixed $needle [, int $offset = 0])
Stripos ()	Finds the position of a character in a string that appears first, not case-sensitive	int Stripos (string $haystack, string $needle [, int $offset])
Strrpos ()	Find the last occurrence of a character in a string	int Strrpos (string $haystack, string $needle [, int $offset = 0])
Strripos ()	Finds the last occurrence of a character in a string, not case-sensitive	int Strripos (string $haystack, string $needle [, int $offset])
STRSPN ()	Returns the length of a substring in a string that first matches mask	int strspn (String $str 1, String $str 2 [, int $start [, int $length]])
STRCSPN ()	Returns the length of a string in a string that does not match mask	int strcspn (String $str 1, String $str 2 [, int $start [, int $length]])
Str_word_count ()	Statistics string contains the number of words	Mix str_word_count (str $str, [])
Strlen ()	Statistical string length	int strlen (str $str)
Count_chars ()	Number of occurrences of all letters in the statistics string (0..255)	Mixed Count_chars (string $string [, int $mode])
MD5 ()	String MD5 encoding	$str = "Hello"; echo MD5 ($STR)
Iconv
Mb_substr	Gets the part of the string	String Mb_substr (string $str, int $start [, int $length = NULL [, String $encoding = Mb_internal_encoding ()]])
Mb_http_output	Set/Get HTTP output character encoding	Mixed Mb_http_output ([string $encoding = Mb_http_output ()])
Mb_strlen	Gets the length of the string	Mixed Mb_strlen (String $str [, String $encoding = Mb_internal_encoding ()])
Iconv	Strings are converted as required character encodings	String Iconv (String $in _charset, String $out _charset, String $str)
Iconv_substr	section that intercepts a string
Iconv_get_encoding	Get internal configuration variables for the iconv extension
Mb_substr_count	Count the number of occurrences of a string
Mb_check_encoding	Checks if the string is valid in the specified encoding
Mb_strrpos	Find where the string last appears in a string
Mb_split	Using regular expressions to split multibyte strings
Parse_url	Interpret the URL as an array

PHP string Common functions