Summary of usage of PHP array operations

PHP definition Array

<?php      $array = [];     $array ["key"] = "value";  ? >

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

1. Declare an array with the array () function.

2. 2. Assign a value directly to the array element.

<?php        //array array    $users = [' A ', ' B ', ' C ', ' d '];    echo $users;//Only print out data type Arra    print_r ($users);//array ([0] = a[1] [b[2] = c[3] + d)    $numbers = Ran GE (1,5);//Create an array containing the specified range    print_r ($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 the string and the number, the array will begin with an array and is represented as a key, Print_ R output Boolean and NULL results are meaningless, so it's more appropriate to use Var_dump

To display all the values in the array through a loop

  for ($i = 0; $i < 5; $i + +) {        echo $users [$i];        Echo ' <br/> ';    }

Count the number of cells in an array or the number of attributes in an object by count/sizeof

for ($i = 0; $i < count ($users); $i + +) {        echo $users [$i];        Echo ' <br/> ';    }

You can also iterate through the array through the Foreach loop, which is the benefit of not having to consider key

foreach ($users as $value) {    echo $value. ' <br/> ';//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. ' <br/> ';//Output Key}?>

Creating an array of custom keys

<?php    //Create a custom array    $array = ["A" =>1, "B" =>2, "C" =>3, "D", "E"];    If there is no declaration key, it will start from zero    print_r ($array);//array ([A]=>1,[b]=>2,[c]=>3,[0]=>d,[1]=>e); >

each () use

 <?php//Create an array $array [' key '] = 22 by assigning a value to a set of elements; echo $array. ' <br/> ';//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//EAC        H returns the current key/value pair in the array and moves the array pointer forward one step $users = Array (' key ' =>22, ' key1 ' =>20, ' Key2 ' =>30); Print_r (each ($users));//array ([1] = [value] = [0] = = Array[key] = array)//equivalent to: $a = array (    [0]=>array,[1]=>22,[value]=>22,[key]=>array]; $a = each ($users);//each the first element of the original array and wraps it into a new array and assigns a value to $ A echo $a [0];//array//!! Represents the conversion of real data to a Boolean value echo!! each ($users);//1; 

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. ' <br/> ';//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

Note: count () and sizeof () count the number of array subscripts
Array_count_values () counts the number of subscript values in an array

<?php        $numbers = Array (' + ', ' 2 ');       Sort ($numbers, sort_string);//Sort by string, string only compares first bit size        print_r ($numbers);//array ([0] = [1] = 2)        $arr = Array (' TRIGKIT4 ', ' banner ', ' Ten ');        Sort ($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 array

        $arr 1  = Array (' Ten ', 2);     $arr 2  =  & $arr 1;     $arr 2 [] =  4;  $arr 2 were changed, $arr 1 is still an Array (' 3 ',//array),     Print_r ($arr 2), and ([0] = [1] = 2 [2] = 4)

Use of Asort

$arr 3  = & $arr 1;//Now ARR1 and ARR3 are the same  $arr 3 [] =  ' 3 ';  Asort ($arr 3);//Sort the array and retain the original relationship  Print_r ($arr 3);//Array ([1] = 2 [2] = 3 [0] + 10)

Use of Ksort

  $fruits = Array (' c ' = = ' banana ', ' a ' = = ' Apple ', ' d ' = ' orange ');   Ksort ($fruits);   Print_r ($fruits);//array ([A] = Apple [c] = banana [d] = orange)

Use of Unshift

    Array_unshift ($array, ' z ');//Add an element  Print_r ($array) at the beginning,//array ([0] = Z [1] = a [2] = = b [3] = c [4] =& Gt d [5] = 0 [6] = 1)

Use of current (POS)

  Echo current ($array);//z; Gets the active cell in the current array

Use of Next

Echo Next ($array); Move the inner pointer in the array forward//a one

Use of Reset

echo Reset ($array);//z the inner pointer of the array to the first cell

Use of Prev

  Echo Next ($array);//a;   Echo prev ($array);//z; pour back a

sizeof uses        echo sizeof ($array);//7; counts the number of array elements    //array_count_values        $num = Array (10,20,30,10,20,1,0,10 )///statistics array element occurrences        print_r (array_count_values ($num));//array ([Ten] = 3 [] = 2 [+] = 1 [1] = 1 [0] =&G T 1)?>

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

For loop traversal

<?php       $value = range (0,120,10);        for ($i =0; $i <count ($value), $i + +) {        print_r ($value [$i]. ' ');//0-ten-A-     }?>

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_pad (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 ' <br/> ';            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 ' <pre> ';             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, $array);        Print_r ($newArray);//array ([1] = I [2] + Am [3] = = A [4] + = PHP [5] = er)         ?>

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        echo $color [1]; Blue?>

Array_unique to delete duplicate values in an array

<?php        $color =array ("Red", "green", "blue", "yellow", "blue", "green");        $result = Array_unique ($color);        Print_r ($result);//array ([0] = red [1] = green [2] = blue [3] = yellow)?>

Array_flip () Exchange the key values and values of an array

  <?php       $array = Array ("Red", "Blue", "Red", "Black");        Print_r ($array);        echo "<br/>";        $array = Array_flip ($array);//        Print_r ($array);//array ([Red] = 2 [Blue] = 1 [Black] = 3)?>

Array_search () Search value

<meta charset= "Utf-8" >    <?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                 }    ?>