Definition and filling of arrays for PHP learning_PHP tutorial

PHP arrays, to put it bluntly, mean that each array of associated data is saved in the form of [index, value]. The index defaults to a number starting from 0. When no index is specified, PHP will automatically generate the index starting from 0. When specifying an index, PHP will start at the integer next to the largest positive integer at the index you specify. If you specify a decimal, PHP will take the integer part as the index.

In addition, let’s talk about some other little things about arrays:
array() can declare an empty array;
array[] = $value appends a data when the array exists; when the array does not exist , generate an array, and append data.
array[$index] = $value When the array exists, append or modify a piece of data; when the array does not exist, generate an array and append the data.

Look at the code below:

Copy code The code is as follows:

//Declare array
$test01 = array();
//Append data
$test01[] = "a"; // array(0 => "a");
//Append an index of "a" ", the data is "b"
$test01["a"] = "b"; // array(0 => "a", "a" => "b");
// Modify the data with index 0
$test01[0] = "c"; // array(0 => "c", "a" => "b");
// Another A declaration method
$test02 = array("a", "b", "c"); // array(0 => "a", 1 => "b", 2 => " c");
// Although a string indexed data is declared, the default index still starts from 0
$test03 = array("a" => "a", "b", "c "); // array("a" => "a", 0 => "b", 1 => "c");
// The largest index in the declaration is 2, although most recently The index is 0, but the default index still starts from 3
$test04 = array(2 => "a", 0=>"b", "c"); // array(2 => "a ", 0 => "b", 3 => "c");
// Declaring a decimal index will take the integer part; when specifying the index, the previously declared value will be modified
$test05 = array("a", 2.7=>"b", 0=>"c"); // array(0 => "c", 2 => "b");
// Although A negative index is declared, but the default index still starts from 0
$test06 = array(-2 =>"a", "b", "c"); // array(-2 => "a" , 1 => "b", 2 => "c");
// Definition of multi-dimensional array
$test07 = array($test01, $test02, $test03);

Then we will introduce some filling functions of arrays. Most of these can be found in the manual, so we will only give a brief introduction.
range($n, $m); specifies the range of values. For example, range(2,4) generates array array(2,3,4).
count($array); Get the size of the array.
array_pad($array, $length, $value); Returns an array with a length of $length. The original array is supplemented by $value, and the length is enough to return the original array.

http://www.bkjia.com/PHPjc/323146.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/323146.htmlTechArticlePHP’s array, to put it bluntly, is that each array of associated data is saved in the form of [index, value] of. The index defaults to a number starting from 0. When no index is specified, PHP will start from 0...