The most comprehensive introduction to PHP arrays

This article mainly on the PHP array has a general introduction, the language is simple, but very comprehensive, hoping to let the beginner PHP small partners have a clearer understanding.

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: One is to apply an array () function declaration, and one is to assign a value directly to the 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$array=array ("1" = "series", "2" = "Cheng", "3" + "CI", "4" and "code");p Rint_r ($array); echo "<br>"; echo $ ARRAY[1]; Note: The subscript defaults to      echo $array [2] starting from 0.       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"; $array [3]= "PHP";p rint_r ($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 achieved through 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 the syntax: Print_r (mixed Expression_r), The parameter expression_r is a normal shape, character, or real variable that 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 logon information while (list ($name, $value) =each ($_post)) {if ($name! = "Submit") {   echo "$name = $value <br>" ;}}

?>
Vii. number of elements in the statistics array
In PHP, use the count () function 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, and mode is an optional parameter, if the Count--recursive is selected ( or 1), this function recursively sets an array of arrays. Such as

<?php$array = Array ("php" = = Array ("PHP function Reference", "PHP Program Development Sample Treasure", "PHP Database system Development Complete Manual"),               "asp" = = Array (" ASP Experience Skills ")         ); Declares a two-dimensional array       echo count ($array, count_recursive);//recursively counts the number of elements in the array, running the result as 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);p rint_r ($array); echo "<br>" Asort ($array);p rint_r ($array);? >

Operation Result:
Array ([ASP] = 3 [JSP] = 2 [PHP] + 1)
Array ([PHP] = 1 [jsp] = 2 [ASP] + 3)

The above eight aspects of the simple introduction of the PHP array of the definition of the structure and methods, and so on, I hope to help you, about the array of problems in the follow-up will collate more corresponding tutorial articles.