PHP string common functions

Arrays, strings and databases are the three most commonly used types of functions in our functions. We have not talked about arrays and databases yet. We will explain them in detail when we talk about them.

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

1. Single-byte string processing function

2. Multi-byte string processing function

3. String encoding conversion function

Let’s talk about why we need to learn so many functions:

1. What we learn is Chinese, which is double-byte or three-byte. Foreigners' functions can only handle single-byte strings such as English and numbers, but not Chinese. It cannot meet our functional requirements

2. Sometimes it is necessary to convert between different character encodings, for example: convert GBK to UTF-8

3. These English characters are not displayed on the computer Here are the

that must be processed. Therefore, we need to learn three types of commonly used string functions.

Let’s post a link to the PHP manual for everyone to see:

http://php.net/manual/zh/

Look Are you frightened by the manual in this link?

Of course, you don’t need to learn so much. PHP Chinese website has helped you prepare the most commonly used ones that require mandatory litigation.

I have taught you how to use it before, so you can start memorizing functions.

Commonly used functions in PHP:

##str_pad()Pall the string to the specified length$str = "Hello World "; echo str_pad($str,20,".");##str_repeat()str_split()strrev()wordwrap()str_shuffle()parse_str()##number_format()Format numbers by thousands grouping"echo number_format("1000000 "); echo number_format("1000000",2); echo number_format("1000000",2,"","",""."");"Convert the string to lowercasecharacter Convert the string to uppercaseThe first letter of the string is capitalizedConvert the first character of each word in the string to uppercaseConvert characters to HTML entitiesConvert predefined characters to html encoding##strcasecmp() Compare two strings without case sensitivityecho strcasecmp("Hello world!","HELLO WORLD!");strcmp( )Compare two strings case-sensitivelystrncmp()Compare the first n characters of the string Characters, case sensitive##strripos()Find the last occurrence of a character in a string, case-insensitiveint strripos ( string $haystack , string $needle [, int $offset ] )strspn()Returns the first string that matches mask Substring lengthint strspn ( string $str1 , string $str2 [, int $start [, int $length ]] )strcspn()Return the length of the string that does not match the maskint strcspn ( string $str1 , string $str2 [, int $start [, int $length ]] )str_word_count()Count the number of words contained in a stringmix str_word_count(str $str,[])strlen()Count string lengthint strlen(str $str)count_chars()Count characters Number of occurrences of all letters in the string (0..255)mixed count_chars ( string $string [, int $mode ] )md5()String md5 encoding$str = "Hello"; echo md5($str)iconvmb_substrGet the part of the stringstring mb_substr ( string $str , int $start [, int $ length = NULL [, string $encoding = mb_internal_encoding() ]] )mb_http_outputSet/get HTTP output character encodingmixed mb_http_output ( [ string $encoding = mb_http_output() ] )mb_strlenGet the length of the stringmixed mb_strlen ( string $str [, string $ encoding = mb_internal_encoding() ] )iconvThe string is converted according to the required character encodingstring iconv ( string $in_charset , string $ out_charset , string $str )iconv_substrIntercept part of the stringiconv_get_encodingGet iconv extended internal configuration variables##mb_substr_countmb_check_encodingmb_strrposmb_splitparse_url

Note: mb_* and iconv_* can handle multi-byte characters, such as Chinese.

---

Chinese mainly uses two encoding formats: GBK and utf-8.
GBK and utf-8 are two different encoding committees’ standards for encoding Chinese characters.

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

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Function name	Description	Instance
trim()	Remove spaces or other predefined characters at both ends of the string	"$str = "\r\nHello World!\r\n"; echo trim($str);
#rtrim()	Remove spaces or other predefined characters on the right side of the string	"$str = "Hello World!\n\n"; echo rtrim ($str);"
chop()	alias for rtrim()	Same as above
ltrim()	Remove spaces or other predefined characters on the left side of the string	"$str = "\r\nHello World!"; echo ltrim($str);"
dirname()	Return to the directory part of the path (we put it in the string function)	echo dirname("c: /testweb/home.php");
Reuse the specified string	echo str_repeat( ".",13);
Split the string into an array	print_r(str_split("Hello")) ;
Reverse the string	echo strrev("Hello World!");
Wrap the string according to the specified length	"$str = ""An example on a long word is: Supercalifragulistic""; echo wordwrap( $str,15);"
Randomly shuffle all the characters in the string	echo str_shuffle("Hello World" );
Parse the string into a variable	"parse_str("id=23&name=John%20Adams",$myArray ); print_r($myArray);"
		##strtolower( )
echo strtolower("Hello WORLD!");		strtoupper()
echo strtoupper("Hello WORLD!");		ucfirst()
echo ucfirst("hello world");		ucwords()
echo ucwords ("hello world");		htmlentities()
$str = ""John & 'Adams' ""; echo htmlentities($str, ENT_COMPAT);		htmlspecialchars()
nl2br()	\nEscaped as tag	echo nl2br("One line.\nAnother line.");
strip_tags()	Strip HTML, XML and PHP tags	echo strip_tags("Hello world!" );
addcslashes()	Add a backslash before the specified character to escape the characters in the string	$str = ""Hello , my name is John Adams." echo $str; echo addcslashes($str,'m');"
stripcslashes()	Deleted by addcslashes() Added backslashes	echo stripcslashes("Hello, \my na\me is Kai Ji\m.");
addslashes()	Add backslashes before specifying predefined characters	$str = "Who's John Adams?";echo addslashes($str);
stripslashes()	Remove escape characters added by addslashes()	echo stripslashes("Who\'s John Adams?");
quotemeta()	Add a backslash before some predefined characters in the string	$str = "Hello world. (can you hear me?)"; echo quotemeta($str);
chr()	Returns characters from the specified ASCII value	echo chr(052);
ord()	Return the ASCII value of the first character of the string	echo ord("hello");
strncasecmp()	Compares the first n characters of the string, case-insensitive	int strncasecmp ( string $str1 , string $str2 , int $len )
strnatcmp()	Natural order method compares string length, case-sensitive	int strnatcmp ( string $str1 , string $str2 )
strnatcasecmp()	Natural order method compares string length, case-insensitive	int strnatcasecmp ( string $str1 , string $str2 )
chunk_split()	Split the string into small chunks	str chunk_split(str $body[,int $len[,str $end]])
strtok()	Cut the string	str strtok(str $str,str $token)
explode()	Use one string as a symbol to split another string	array explode(str $sep,str $str[,int $limit ])
implode()	Same as join, concatenate the array values ​​into a string using predetermined characters	string implode ( string $glue , array $pieces )
substr()	Intercept string	string substr ( string $string , int $start [, int $length ] )
str_replace()	String replacement operation, case sensitive	mix str_replace(mix $search,,mix $replace,mix $subject [,int &$num])
str_ireplace()	String replacement operation, case-insensitive	mix str_ireplace ( mix $search , mix $replace , mix $subject [, int &$count ] )
substr_count()	Count 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 certain string in the string with another string	mixed substr_replace (mixed $string, string $replacement, int $start [, int $length])
similar_text()	Returns the number of identical characters in the two strings	int similar_text(str $str1,str $str2)
strchr( )	Returns the string from the beginning to the end of a string in another string	string strstr (string $str, string $needle, bool $before_needle)
strrchr()	Returns a string starting from the last occurrence of a string in another string to the end	string strrchr ( string $haystack , mixed $needle )
stristr()	Returns a string from the beginning to the end of another string, case-insensitive	string stristr ( string $haystack , mixed $needle [, bool $before_needle = false ] )
strtr()	Convert some characters in the string	string strtr ( string $str , string $from , string $to )
strpos()	Find the first character in the string Appearance position	int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )
stripos()	Find the first occurrence of a character in a string, case-insensitive	int stripos ( string $haystack , string $needle [, int $offset ] )
strrpos()	Find the last position of a character in a string	int strrpos ( string $haystack , string $needle [, int $offset = 0 ] )
Count the number of occurrences of a string
Check whether the string is valid in the specified encoding
Find the last occurrence of a string in a string
Use regular expressions to split multi-byte strings
Interpret the URL into an array