mySQL traverse string PHP string common sense

Pay attention to the use of escape characters\,",$
Pay attention to the use of octal or hexadecimal characters to represent xf6
echo "Hxf6me";//You need to check whether this type of text encoding is supported
--------- ------------Output results------------------------------------ ----
H鑇e
----------------------------------------- ----------------------------
1. Use printf() and sprintf() to create formatted output
printf() direct output To the output buffer
The output of sprintf() is returned as a string
For example, printf("Output content%.2fn",$PI());
All conversion specifications start with %
Data types include d-integer, s -String, f-floating point number, b-binary
.2 is an optional width indicator, and the output to the right of the decimal point is padded with 0
printf("%.2f",3.14159);
printf("%10.2f", 3.14159);
printf("%.10f",3.14159);
printf("%.9s",abcdefghijklmn);
printf("%5.2f,%f,%7.3fm",3.14159,3.14159,3.14159);
printf("%b %d %f %s n",123,123,123,"test");
------------------------Output results----- ----------------------------------
3.14 3.143.1415900000abcdefghi 3.14,3.141590, 3.142m1111011 123 123.000000 test
-------------------------------------------------- ------------------
2. String padding
string str_pad(string input original string, int length the total length after adding [, string padding characters to be filled [, int pad_type] padding type])
The padding type is added to the left STR_PAD_LEFT, the default is added to the right, and padding is added to both ends STR_PAD_BOTH
$index = array("one"=>1,"two"=>155, "three"=>1679);
echo "
";
echo str_pad("This is the title",50," ",STR_PAD_BOTH)."n";
foreach($index as $inkey=>$inval )
echo str_pad($inkey,30,".").str_pad($inval,20,".",STR_PAD_LEFT)."n";
echo "
";
--------- ----------Output results---------------------------------------- ---
This is the title
one...................................... .....1
two........................................ ..155
three........................................1679
-- -------------------------------------------------- ------------------
string strtolower(string subject)//Convert to lowercase
string strtoupper(string subject)//Convert to uppercase
string ucfirst(string subject)// Capitalize the first letter of each word
string ucwords(string subject)//Capital the first letter of each word
string ltrim(string subject)//Remove the left blank
string rtrim(string subject)//Remove the right blank
string trim(string subject) Left and right whitespace, whitespace includes null, tab character, newline character, carriage return character and space
string n12br(string source)//Convert the newline character represented by n to
mark
3. String comparison
integer strcmp(sting str1 , string str2) //str1 is greater than str2 and returns -1. str1 is less than str2 and returns 1. If str1 and str2 are equal, return 0.
integer strmcmp(sting str1, string str2, integer length) //The third parameter limits the comparison of length characters.
print strcmp("aardvark","aardwolf");
print strncmp("aardvark","aardwolf",4);
---------------------Output results ----------------------------------------
-10
------ -------------------------------------------------- -------------
strcasecmp() and strncasecmp() are case-insensitive comparison functions
4. Find and extract substrings
string substr(sting source,integer start[,integer length])//Take length characters from start
start and length can use negative values
$var = "abcdefgh";
print substr($var,2);//Start counting from 0
print substr($var ,2,3);
print substr($var,-1);//Start from the end of the string
print substr($var,-5,2);
print substr($var,-5,-2 );
---------------------Output result------------------------ ----------------
cdefgh
cde
h
de
def
----------------------- -----------------------------------------------
integer strpos( string haystack,string needle[,integer offset])//Find the position of the substring and return the first occurrence.
integer strrpos(string haystack,string needle)//Only search for a single character (only take the first for multiple characters ), returns the index of the last occurrence.
There are also common functions for extracting the found part from a string
string strstr(string haystack,string needle)//It is not case sensitive
string stristr(string haystack,string needle) )//Case sensitive
string strrchr(string haystack,sting needle)
**************** array explode(string separator,string subject[,integer limit])//Return a string array
array implode(string glue,array pieces)//Return a string
////////////////////////////Code segment///// /////////////////////////////////////
$guest = "this is a string";
$guestArray = explode(" ",$guest);
var_dump($guestArray);
sort($guestArray);
echo implode(",",$guestArray);
/////////////// ///////////////////////////////////////////////////// ////////
------------------------Output results------------------ -----------------------
array(4) { [0]=> string(4) "this" [1]=> string(2 ) "is" [2]=> string(1) "a" [3]=> string(6) "string" }a,is,string,this
------------------------------------------------ -----------------------------
5. Replace characters and substrings
string substr_replace(string source,string replace,int start[,int length])

The above introduces the common sense of mySQL traversing strings and PHP strings, including the content of mySQL traversing strings. I hope it will be helpful to friends who are interested in PHP tutorials.