Introduction to commonly used array functions in PHP, php array functions_PHP tutorial

Introduction to commonly used array functions in PHP, php array functions

It is indispensable to consult manuals in programming, so you must learn to use existing things. For example, the array processing function in PHP already has a sorting function. Why bother to write something that is fake? Soak or stack or quick queue.

Programming is an indirect process and a process of reuse. To write good code, design patterns are indispensable for support. It may be difficult for beginners to learn design patterns (just like when I first looked at design patterns, It’s really a bit laborious), but when you have accumulated a certain amount of code, when you study design patterns, you feel that design patterns are really useful and can help you write beautiful code. Having said that, I got a little off track, so let’s summarize the commonly used functions for array operations in PHP.

Some readers may feel that the commonly used functions for arrays summarized below are a bit lacking. Will the flames be high if everyone adds firewood? If you feel that there are other commonly used array processing functions, please leave a comment. Don’t be stingy with your knowledge. , isn’t it a very happy thing to share things with others? Also, the following code is from my own hand, but it was written two years ago. Everyone is welcome to criticize and correct me.

array_splice() deletes the specified element in the array

array_splice (array name, number of items to delete from front to back, new size of an array); without the third parameter, there is no returned array. When there is no third parameter, the meaning of the second parameter is from front to back. Keep a few

exp:

<&#63;php
  $my_array=array(  //建立数组
    "hehe"=>"haha",
    "A"=>"lu",
    "lu"=>"ge"
  );
  $new=array_splice($my_array,1,3);  //使用array_splice(数组名，从前往后删的个数，new一个数组的大小);
  var_dump($new);
&#63;>

Result: array(2) { ["A"]=> string(2) "lu" ["lu"]=> string(2) "ge" }

2. Traversal of foreach() array

Usage: foreach (array as key name => key value) or foreach (array as key value)

exp:

<&#63;php
  $my_array=array(  //建立数组
    "hehe"=>"haha",
    "A"=>"lu",
    "lu"=>"ge"
  );
  foreach($my_array as $key=>$value)
  {
    echo $key."=>".$value."<br/>";
  }
&#63;>

Output result:

hehe=>haha

A=>lu

lu=>ge

3. Sorting of arrays

(1) sort() and rsort() Sort by key value sort() from small to large, rsort() from large to small

sort () exp:

<&#63;php
  $my_array=array(1,2,3,6,7,8,9,4,5);//建立数组
  sort($my_array);
  foreach($my_array as $keys=>$value)
  {
    echo $keys."=>".$value."<br/>";
  }
&#63;>

Output result:

  0=>1

  1=>2
  2=>3
  3=>4
  4=>5
  5=>6
  6=>7
  7=>8
  8=>9

rsort() exp:

<&#63;php
  $my_array=array(1,2,3,6,7,8,9,4,5);//建立数组
  rsort($my_array);
  foreach($my_array as $keys=>$value)
  {
    echo $keys."=>".$value."<br/>";
  }
&#63;>

Output result:

  0=>9
  1=>8
  2=>7
  3=>6  
  4=>5
  5=>4
  6=>3
  7=>2
  8=>1

(2).asort() and arsort() have the same principle as above, but do not change the corresponding relationship between key names and key values ​​

exp:

<&#63;php
  $my_array=array(1,2,3,6,7,8,9,4,5);//建立数组
  asort($my_array);
  foreach($my_array as $keys=>$value)
  {
    echo $keys."=>".$value."<br/>";
  }
&#63;>

Output result:

0=>1
1=>2
2=>3
7=>4
8=>5
3=>6
4=>7
5=>8
6=>9

(3)ksort() and krsort() are sorting by key name

4. Mathematical functions of arrays

array_sum() calculates the sum of all key values ​​in the array count() calculates the number of elements

exp:

<&#63;php
  $my_array=array(1,2,3,6,7,8,9,4,5);//建立数组
  echo array_sum($my_array);
&#63;>

Output result: 45

5. Other functions

array_unique() removes identical elements from an array

in_array() checks whether a value is in the array (returns true and false)

array_search() returns the key or value, and returns the key name corresponding to the key value

shuffle() disrupts the original array

<&#63;php
  $my_array=array(1,2,3,6,7,8,9,4,5,5,5,5);//建立数组
  array_unique($my_array);//去除数组中的相同元素
  var_dump($my_array);
  echo "<br/>";
  echo in_array(5,$my_array);
  echo "<br/>";
  $new=array_search(6,$my_array);//返回的是键值所对应的键名
  echo $new;
&#63;>

Output result:

array(12) { [0]=> int(1) [1]=> int(2) [2]=> int(3) [3]=> int(6) [4]=> int(7) [5]=> int(8) [6]=> int(9) [7]=> int(4) [8]=> int(5) [9]=> int(5) [10]=> int(5) [11]=> int(5) } 
1
3

foreach (array_expression as $key => $value)
key() function is used to read the index value of the data pointed to by the current pointer. current() is used to obtain the content data of the current pointer position.
count() function Will return the length value of the target array
The control function of the array pointer
pnext(), prev(), end() and reset()
next() is responsible for moving the pointer backward, prev() Responsible for moving the pointer forward; end() will point the pointer to the last element in the array, and the reset() function will unconditionally move the current pointer to the first index position.
in_array(mixed $needle, array $haystack[, bool $strict]); Determine the existence or absence of an array element.
array_search(), this function returns the corresponding key name. The array_key_exists() function can retrieve whether a given key name (index) exists in the array.

Also, I can give you PPT if needed

In fact, there is no need to search everywhere for so-called "commonly used functions". The so-called "commonly used functions" vary from person to person. Someone often uses a certain function, but it does not mean that you will also use it frequently. There are many PHP functions. It is key to always have a PHP help manual. If you encounter something you are not familiar with, check it out. The more times you check it, the more often it will become "commonly used".

Generally speaking, string, array, and database class functions are relatively commonly used categories.

The functions are listed below for reference only.

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//================================Time and Date========= ======================
//y returns the last two digits of the year, the four-digit number of year Y, the number of month m, and the English month of M. d number of the month, D day of the week in English
$date=date("Y-m-d");

//include,include_once.require,require_once
//require("file.php" ) Before the PHP program is executed, the files specified by require will be read in. If an error occurs, it will be fatal.
//include("file.php") can be placed anywhere in the PHP program. The file specified by include will not be read until the PHP program is executed. If an error occurs,

//= ==============================Output printing================== =============
//sprintf("%d","3.2") ;//Only formatting, return the formatted string, no output.
//printf("%d","3.2") ;//Formatting and output
//print("3.2") ;//Only output
//echo "nihao" ,"aa";//Can output multiple strings
//print_r(array("a","b","c"));//Display the key values ​​and elements of the array in sequence

//============================== Commonly used string functions========== =====================

//Get the length of the string, how many characters there are, spaces are also counted
$str=" sdaf sd ";
$len=strlen($str);

//Use the string in the first parameter to connect each element in the subsequent array and return a string.
$str=implode("-",array("a","b","c"));

//String splitting method, returns an array, using the first parameter The characters in will split the following string, and intercept the characters before, after, and between the specified characters. If the specified character is at the beginning or end, the element at the beginning or end of the returned array will be an empty string
//If it is not divided into a string, Returns a null value to the corresponding element of the array. The last limit returns the length of the array. If there is no limit, it will continue to be divided.
$array=explode("a","asdd...the rest of the text>>