Summary of how PHP arrays are used

An array is a set of data that organizes a series of data to form an operational whole. Each entity of an array contains two items: A key and a value.

First, what is an array
An array is a set of data that organizes a series of data to form an operational whole. Each entity of an array contains two items: A key and a value.
II. Statement of data
There are two main ways to declare an array in PHP:
The first is to apply an array () function declaration ,
One is to assign a value directly to the array element .
The <1>array () function declares an array of ways in which the syntax of the [mixed] parameter mixed is Key=>value
Such as

<?php
$array =array ("1" = "series", "2" = "Cheng", "3" = "CI", "4" and "Code");
Print_r ($array);
echo "<br>";
echo $array [1]; Note: The subscript default is starting from 0
Echo $array [2];
Echo $array [3];
Echo $array [4];
?>

<2> assigns a value directly to an array element.
If you do not know the size of the array created when you create the array, or if the size of the array may change when you actually write the program, the method used to create this array is preferable.
Such as

<?php
$array [1]= "I";
$array [2]= "Love";
$array [3]= "PHP";
Print_r ($array); Output the structure of the created array
?>

Iii. Types of arrays
PHP supports two arrays : an indexed array (indexed array) and a union array (associative array), which uses a number as the key, which uses a string as the key.
Iv. Output Arrays
The output of an array element in PHP can be implemented with Echo and print statements, but this can only be output from an element in an array, and the print_r () function is used to output the structure of the arrays, with its syntax: Print_r (mixed expression), the parameter expression is a normal shape, a character type, or a real variable outputs the variable itself, and if the parameter is an array, all the elements in the array are displayed in the order of key values and elements.
V. Construction of arrays
One-dimensional arrays:
When an element of an array is a variable, it is called a one-dimensional array.
Declares an array: type specifier array name [constant expression];
Two-dimensional arrays:
When an element of an array is an array, it is called a two-dimensional array.
Such as

<?php
$str = Array (
"Network programming language" =>array ("PHP", "JSP", "ASP"),
"Sports" =>array ("M" = "Football", "n" = "basketball");
Print_r ($STR);
?>

Vi. iterating through an array
Iterating through all the elements in an array is a common operation that can be done during the traversal of a query or other function. There are several ways to iterate through an array in PHP, and the two most commonly used methods are described below.
<1> iterating through an array using the foreach structure;
<2> using the list () function to iterate through an array, the list () function can only be used for arrays of numeric indexes, and the numeric index starts at 0.
Example: Comprehensive use list () and each () authenticated user login:

<?php
Output User Login information
while (list ($name, $value) =each ($_post)) {
if ($name! = "Submit") {
echo "$name = $value <br>";
}
}
?>

Vii. number of elements in the statistics array
In PHP, the count () function is used to count the number of elements in the array, with the syntax:int coun (mixed array[,int mode]), where the parameter array is the necessary parameter, mode is an optional parameter, If Count--recursive (or 1) is selected, this function recursively sets an array of arrays. Such as

<?php
$array = Array ("php" = = Array ("PHP function Reference", "PHP Program Development Sample Treasure", "PHP Database system Development Complete manual"),
"ASP" = = Array ("ASP experience Skill Treasure")
); Declaring a two-dimensional array
echo Count ($array, count_recursive);//The number of elements of the recursive statistic array, with a run result of 6
?>

Eight, array sorting
<1> use Sort () and rsort () to order ascending and descending pairs of arrays, for example,
<?php
$array =array (5,26,37,18,9,42,88,66);
$array 1=sort ($array);
for ($i =0; $i <count ($array); $i + +) {
echo $array [$i]. " ";
}
echo "<br>";
$array 1=rsort ($array);
for ($i =0; $i <count ($array); $i + +) {
echo $array [$i]. " ";
}
?>
Operation Result:
5 9 18 26 37 42 66 88
88 66 42 37 26 18 9 5
<2> sorting associative arrays using Ksort () and Asort ()
If a related array is used, the ordering of the keywords and values remains consistent after sorting, which is required using the Ksort () and Asort () letters
Number, such as,
<?php
$array =array (' php ' =>1, ' jsp ' =>2, ' ASP ' =>3);
Ksort ($array);
Print_r ($array);
echo "<br>";
Asort ($array);
Print_r ($array);
?>
Operation Result:
Array ([ASP] = 3 [JSP] = 2 [PHP] + 1)
Array ([PHP] = 1 [jsp] = 2 [ASP] + 3)

Summary of how PHP arrays are used