Php array-related processing functions and str string processing and regular expressions

Array-related processing functions:

1) array key-value operation functions
 
Array_values (); // obtain the value in the array
Array_keys (); // Obtain the keys in the array
In_array (); // check whether a value is in the array
Array_key_exists (); // check whether a key is in the array
Array_flip (); // key and value pairs
Array_reverse (); // reverse the value in the array

2) calculate the element and uniqueness of the array.

Count (); // count the number of arrays
Array_count_values (); // number of occurrences of the median in a statistical group
Array_unique (); // delete duplicate values in the array

3) use the callback function to process array functions
 
Array_filter (); // array value filtering
Array_map (); // calls the callback function to the unit of the given array.

4) sorting functions of arrays

 
Sort ();
// Sort the array values by value, in ascending order, without retaining the key
Rsort ();
// Sort the array values by value. The values are sorted in descending order and keys are not retained.
 
Asort ();
// Sort the array values by value, sort them in ascending order, and retain keys
Arsort ();
// Sort the array values by value, sort them in descending order, and retain keys
 
Ksort ();
// Sort the array values by pressing the key in ascending order and retain the key
Krsort ();
// Sort the array values by pressing the keys in descending order and retain the keys.
 
Natsort ();
// Sort by natural number
Natcasesort ();
// Ignore case-insensitive natural numbers for sorting
 
Array_multisort (); // sort another array with an array
SORT_DESC reverse order
SORT_ASC positive Order array_multisort ($ arr2, SORT_DESC, $ arr );

5) split, merge, decompose and combine functions

 
Array_slice (); // capture a segment of value $ arr2 = array_slice ($ arr,); 0 start position, 3, return value: intercepted content
 
Array_splice (); // extract a value and retain a value
 
Returned value: the remaining content after the truncation // array_splice (3, 3, "aa"); 3 values are truncated from the position of subscript 3, and aa replaces the intercepted content.
 
Array_combine (); // merge. One is the key, and the other is the value eg: $ arr3 = array_combine ($ arr1, $ arr2); $ arr1 is the key value, and $ arr2 is the value.
 
Array_merge (); Union set // merge, with the same key value. A new array $ arr3 = array_merge ($ arr1, $ arr2) is returned before overwriting );
 
Array_intersect (); // intersection
 
Array_diff (); // difference set
 
Implode (); // concatenate the array into a string such as: $ str = implode ("|", $ arr); | delimiter
  
Explode (); // splits the string into an array eg: $ arr = explode ('|', $ str );

6) array and data structure

 
Array_pop (); // The Last pop-up value, returns the pop-up value // unset ($ arr [count ($ arr)-1]);
Array_push (); array_push ($ arr, 6); // add a value from the end and return the number of arrays.
// $ Arr [] = "aa ";
Array_shift (); // A value is popped up from the front, and the removal value is returned. The original array subscript is rearranged.
// Unset ($ arr [0]); original array subscript is not rearranged
Array_unshift (); // insert a value from the front to return the number of arrays.

7) other useful array processing functions

 
Array_rand (); // random key
 
Shuffle (); // disrupt the array
 
Array_sum (); // sum of all values in the array
 
Range (); // Obtain an array in the specified range.
// Range (); returns the array (, 3,..., 10 );
// Range (, 2); array (, 9); 2 indicates the difference value; the default value is 0.

String Processing and regular expressions
----------------

1. Introduction to string processing
2. Common string output functions
3. Common string formatting functions
4. String comparison functions
5. Application of regular expressions in strings
6. perl-compatible regular expression functions

String output:

 
1) echo "hello world www.111cn.net ";
2) print "aaaa ";
3) die ("output an error message ");
4) printf ("-- % s ---- % s --", $ a, $ B );
% S string
% D number
% F floating point // %. 2f two digits after the decimal point
5) sprintf ("$ s % s", $ a, $ B );
Instead of directly outputting, the returned value is a new variable.

Common string formatting functions:
1. Remove spaces and string filling functions
 
Ltrim () // remove the left space
Rtrim () // remove the right space;
Trim () // remove the two spaces $ str = 'abc'; trim ($ str, 'B'); echo $ str; result: ac; the specified string can be deleted.
Str_pad () // add a space or string to the string
 
<? Php
$ Input = "Alien ";
Echo str_pad ($ input, 10); // output "Alien"
Echo str_pad ($ input, 10, "-=", STR_PAD_LEFT); // output "-=-Alien"
Echo str_pad ($ input, 10, "_", STR_PAD_BOTH); // output "_ Alien ___"
Echo str_pad ($ input, 6, "___"); // output "Alien _"
?>

2. String case conversion function

 
Strtolower ()
Strtoupper ()
Ucfirst ()
Ucwords ()

3. String functions associated with html tags

 
Nl2br ()
Htmlspecialchars ()
Strip_tags ()
Addslashes ()
Stripslashes ()

4. Other string formatting functions

 
Strrev ()
Strlen () // returns the length of the string
Number_format ()
Md5 () // unidirectional irreversible encryption
Str_shuffle () // random output string

String comparison functions:
1. Compare strings by byte
1
 
Strcmp ($ str1, $ str2) // compare each byte of a string
 
Strcasecmp () // ignore each byte of the case-sensitive comparison string

2. String comparison by natural sorting

 
Strnatcmp ();
// Compare the numbers in a string in natural order

String segmentation and concatenation:
1. Segmentation
 
// Split the string into an array
Explode ()
Preg_split ('//', $ str );

2. Splicing
// Concatenates an array into a string

 
Implode ()
Join () // equal to implode ();

String truncation:

 
Substr ()

String search:
 
Strstr () // finds the first occurrence of a specified character in a string
 
 
Strrchr () // find the last occurrence of a specified character in the string
 
 
Strpos () // the position where w first appears in $ str
Strrpos ($ str, 'w') // The last position of w in $ str

String replacement:
1
 
Str_replace ()

Supports multi-byte text

 
Mb_substr ($ str, "UTF-8 ");
Mb_strpos ();
Mb_strrpos ();
Mb_strstr ();
Mb_strtoupper ();
Mb_strtolower ();

Application of regular expressions in strings:
I. INTRODUCTION to regular expressions
A regular expression is a syntax rule used to describe character arrangement and matching modes. It is mainly used for character string mode segmentation, matching, search and replacement operations.

A style is generally a procedural description of a text pattern consisting of regular characters and special characters. Here we use perl compatible regular expressions.
II. Regular expression syntax
1. Atom www.111cn.net
1) single character, number
Any character in a-z, A-Z, 0-9 a-z
2) mode unit
(Abc) matches abc and forms a unit.
3) atomic table
[Abc] any one of the characters a, B, or c
4) re-use mode unit
\ 1, $1
5) common escape characters
D, D, w, W, s, S
D. Match a number.
D. Match a non-number.
W matching letters, numbers, and underscores
W in addition to letters, numbers, and underscores
S matches blank characters, spaces, tab
In addition to blank characters, spaces, and tabs
6) convert to metacharacters
*,. []
2. Metacharacters
*, + ,?, |, ^, $, B, B, [], [^], {m}, {m, n}, {m ,},(),.
D * one or more or zero numbers
D + one or more numbers
D? One or zero digits
. Any character
3. Pattern modifier
I, m, s, U, e
I case-insensitive
M is considered as multi-row
S is regarded as a row
U greedy mode, Max mode
E is used for replacement. You can use function processing to reference \ 1, $1.
III. String regular expression functions
1. String matching and searching
Preg_match ()
Preg_match_all ()
Preg_grep ()
2. String replacement
Preg_replace ()
// Problem: regular e modifier <>
3. String segmentation and connection
Preg_split ()
4. web verification application of regular expressions
1) email address
2) url
3) telephone number
 
 
Ubb editor:
 
[Url] [/url] [B] Text [/B]