PHP Common Array Operation method Note collation, array operation method _php tutorial

How to use the array operation method in PHP

Overview
To access the contents of a variable, you can use its name directly. If the variable is an array, you can use a combination of the variable name and keyword or index to access its contents.
Like other variables, you can change the contents of an array element by using operator =. Array cells can be accessed through the Array[key] syntax.

Basic Operations for arrays
PHP definition array:

<?php   $array = Array ();   

There are two main ways to declare an array in PHP:

1. Declare an array with the array () function,
2. Assign a value directly to the array element.

<?php  //array Arrays  $users = Array (' phone ', ' computer ', ' dos ', ' Linux ');  echo $users;//Only print out data type Array  print_r ($users);//array ([0] = phone [1] = computer [2] = = DOS [3] = Linu x)  $numbers = range (1,5);//Create an array containing the specified range  print_r ($numbers);//array ([0] = 1 [1] = 2 [2] = 3 [3] => ; 4 [4] = 5)  Print_r (true);//1  Var_dump (false);//bool (false)//print_r can simply print strings and numbers, Arrays begin with an array and are represented as key values, Print_r output Boolean values and null results are meaningless, so use var_dump to display all values in the array for  ($i = 0; $i < 5; $i + +) {    echo $users [$i];    Echo '
';  } By count/sizeof the number of cells in the array or the number of attributes in the object for  ($i = 0; $i < count ($users); $i + +) {    echo $users [$i];    Echo '
';  } You can also iterate through the array through the Foreach loop, which has the advantage of not having to consider key  foreach ($users as $value) {    echo $value.
';//dot number is a string join symbol  }//foreach loop traversal $key = = $value; $key and $value are variable names, you can set the  foreach ($users as $key + = $value) {    echo $key. '
';//output key  }?>

Creating an array of custom keys

<?php  //Create an array of custom keys  $ceo = Array (' apple ' = ' jobs ', ' microsoft ' = ' Nadella ', ' Larry Page ', ' Eric ');  If you do not declare the key of the element, it will start from zero  print_r ($CEO);//array ([Apple] = jobs [Microsoft] = Nadella [0] = Larry Page [1] =& Gt Eric)  echo $ceo [' Apple '];//jobs   //php5.4 usage  $array = [    "foo" + "Bar",    "bar" and "foo",  ];  Print_r ($array);//array ([foo] = bar [bar] = foo)?>  

From php5.4 you can use the short array definition syntax and replace array () with []. A bit similar to the definition of arrays in JavaScript.

Use of each ()

<?php  //Create an array  $ages [' trigkit4 '] = by assigning a value to a set of elements;  echo $ages. '
';//array  //Because the index of the associated array is not a number, it cannot be traversed by a for loop, only through  the use of the Foreach Loop or list () and each () structure//each/  / Each returns the current key/value pair in the array and moves the array pointer forward one step  $users = Array (' TRIGKIT4 ' =>22, ' Mike ' =>20, ' John ' =>30);  Print_r (each ($users));//array ([1] = [value] = [0] = = TRIGKIT4 [key] = TRIGKIT4)  //equivalent: $a = a Rray ([0]=>trigkit4,[1]=>22,[value]=>22,[key]=>trigkit4);  $a = each ($users);//each the first element of the original array and wraps it into a new array and assigns a value to $ A  echo $a [0];//trigkit4  //!! Represents the conversion of real-world data to a Boolean value  

Each pointer points to the first key-value pair and returns the first array element, gets its key-value pair, and wraps it into a new array

Use of List ()
The list is used to assign the values of the array to some variables, as shown in the following example:

<?php  $a = [' 2 ', ' abc ', ' Def '];  List ($var 1, $var 2) = $a;  echo $var 1. '
';//2  echo $var 2;//abc  $a = [' name ' = ' trigkit4 ', ' age ' =>22, ' 0 ' + ' boy '];  List only recognizes key as the index of the number  list ($var 1, $var 2) = $a;  Echo $var 1;//boy?>

Note: List only knows the index of key as a number

Ordering of array elements
The reverse sort: sort (), Asort (), and Ksort () are both positive and, of course, the corresponding reverse sort.
Implement reverse: Rsort (), Arsort (), and Krsort ().

The Array_unshift () function adds a new element to the array header, and the Array_push () function adds each new element to the end of the array.
Array_shift () deletes the first element of the array header, and its inverse function is array_pop (), deleting and returning an element at the end of the array.
Array_rand () returns one or more keys in the array.

The function shuffle () randomly sorts the elements of an array.
The function Array_reverse () gives a reverse sort of the original array
Use of various types of APIs for arrays
Count () and sizeof () counts the number of array subscripts
Array_count_values () counts the number of subscript values in an array

<?php $numbers = Array (' 100 ', ' 2 '); Sort ($numbers, sort_string);//Sort by string, string only compares first bit size print_r ($numbers);//array ([0] = [1] = 2) $arr = Array (' tr  Igkit4 ', ' banner ', ' 10 ');  Sort ($arr, sort_string);  Print_r ($arr);//array ([0] = [1] = banner [2] = = TRIGKIT4) shuffle ($arr);  Print_r ($arr);//random sort $array = Array (' A ', ' B ', ' C ', ' d ', ' 0 ', ' 1 ');  Array_reverse ($array); Print_r ($array);//reverse order of the original array.  Array ([0] = a [1] = b [2] = = c [3] = d [4] = 0 [5] + 1)//copy of the array $arr 1 = array (' 10 ', 2);  $arr 2 = & $arr 1; $arr 2 [] = 4;  $arr 2 were changed, $arr 1 was still Array ('//array ', 3) Print_r ($arr 2), and the//asort ([0] = [1] = 2 [2] + 4) use $arr 3 =  & $arr 1;//Now ARR1 and ARR3 are the same $arr 3 [] = ' 3 '; Asort ($arr 3);//sorting the array and preserving the original relationship Print_r ($arr 3);//Array ([1] = 2 [2] = 3 [0] = +)//ksort Use $fruits = arr  Ay (' c ' = ' banana ', ' a ' = ' = ' apple ', ' d ' = ' orange ');  Ksort ($fruits); Print_r ($fruits);//array ([A] = Apple [c] = banAna [d] = orange)//unshift use Array_unshift ($array, ' z ');//Add an element Print_r ($array) at the beginning,//array ([0] = Z [1] =&gt ;   A [2] = b [3] = c [4] = + d [5] = 0 [6] = 1)//current (POS) using echo current ($array);//z; Gets the active cell in the current array Next uses echo next ($array);//a the inner pointer in the array moves forward one//reset using echo reset ($array);//z; Pointing the array interior pointer to the first cell//prev using echo NEX  T ($array);//a; Echo prev ($array);//z; Returns a//sizeof using echo sizeof ($array),//7; counts the number of array elements//array_count_values $num = Array (10,20,30,10 , 20,1,0,10);//Count the number of occurrences of an array element Print_r (Array_count_values ($num));//array ([Ten] = 3 [] = 2 [+] = 1 [1] = 1   [0] = 1)?>

Current (): Each array has an internal pointer to his present cell, initially pointing to the first element inserted into the array

For loop traversal

<?php  $value = range (0,120,10);  for ($i =0; $i
 
  

An instance of an array
Use of the Array_pad function

<?php  //array_pad function, array array is selectively appended  $num = Array (1=>10,2=>20,3=>30);  $num = Array_pad ($num, 4,40);  Print_r ($num);//array ([0] = [1] = [2] = [3] = +)  $num = Array_pad ($num, -5,50);//array_pa D (array,size,value)  print_r ($num);//array ([0] = [1] = [2] = [3] = [4] = +)?>

Size: The specified length. Integers are filled to the right, and negative numbers are filled to the left.

Use of unset ()

  use of <?php//unset ()  $num = Array_fill (0,5,rand (1,10)),//rand (Min,max)  print_r ($num);//array ([0] = > 8 [1] = 8 [2] = 8 [3] = 8 [4] = 8)   echo '
';  Unset ($num [3]);  Print_r ($num);//array ([0] = 8 [1] = 8 [2] = 8 [4] = 8)?>

Use of Array_fill ()

Use of <?php//array_fill () $num = Range (' A ', ' e '); $arrayFilled = Array_fill ($num);//array_fill (Start,number,value) echo '
';  Print_r ($arrayFilled);? >
Use of Array_combine ()
<? PHP  $number = Array (1,2,3,4,5);  $array = Array ("I", "Am", "A", "PHP", "er");  $newArray = Array_combine ($number, $array);  
Array_splice () Delete array members
<?php  $color = Array ("Red", "green", "blue", "yellow");  Count ($color); Get 4  Array_splice ($color, 1, 1);//delete the second element  Print_r (count ($color));//3  echo $color [2];//yellow  
Array_unique to delete duplicate values in an array
<?php  $color =array ("Red", "green", "blue", "yellow", "blue", "green");  $result = Array_unique ($color);  
Array_flip () Exchange the key values and values of an array
<? PHP  $array = Array ("Red", "Blue", "Red", "Black");  Print_r ($array);  echo "
";  $array = Array_flip ($array);//  
Array_search () Search value
 
   <?php  $array = Array ("Red", "Blue", "Red", "Black");  $result =array_search ("Red", $array)//array_search (value,array,strict)  if (($result = = = NULL)) {    echo ' There is no value red ";  } else{    echo "presence value $result";//Presence Value 0   
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