Detailed explanation of PHP list(),each(),reset() function application_PHP tutorial

The article introduces the detailed application of PHP list(), each(), and reset() functions. Friends who need to know more can refer to it.

1.list function

The list function assigns the values ​​in the array to some variables. The syntax is as follows:

void list ( mixed $varname, mixed $varname... )

Like array(), this is not a real function, but a language construct. list() assigns values ​​to a set of variables in one operation.

Note: List () can only be used for the array of digital indexes and assume that digital indexes start from 0.

Example 1. list() example

Code:

The code is as follows

Copy code

代码如下	复制代码
$arr=array(1,2,3); list($a,$b,$c)=$arr; echo "$a是$a, $b是$b, $c是$c. "; ?> 显示为： $a是1, $b是2, $c是3.

$arr=array(1,2,3); list($a,$b,$c)=$arr;

echo "$a is $a,
$b is $b,
$c is $c.
"; ?>

displays as:

$a is 1,

$b is 2,

$c is 3. 

Note that the subscript of the list function must be a number and must start from 0.

2.each function and reset function

The

each function returns the current key/value pair in the array and moves the array pointer forward one step. Note that it is a pair. The details are explained below.

The function syntax:

array each ( array &$array )

Returns the key/value pair of the current pointer position in array and moves the array pointer forward. Key-value pairs are returned as a four-element array, key

The values ​​are 0, 1, key and value. Cells 0 and key contain the key names of the array cells, and 1 and value contain the data. If inside

代码如下	复制代码
$arr=array("我是第一个值","我是第二个值","我是第三个值"); echo "当我们用0,1为索引时： "; $a=each($arr); echo "我在$arr数组中的位置为：".$a['0']; echo " "; echo "我在$arr数组中的值为：".$a['1']; echo " "; echo "当我们用key,value为索引时： "; $b=each($arr); echo "我在$arr数组中的位置为：".$b['key']; echo " "; echo "     我在$arr数组中的值为：".$b['value']; ?>

If the pointer crosses the end of the array, each() returns FALSE. Why does each function have four tables below? In fact, each letter

The four subscripts obtained by the number are just for the convenience of our operation. We can use 0, 1 as the index, or key and value as the index.


Example 2: each example

Code:

The code is as follows

Copy code

$arr=array("I am the first value","I am the second value","I am the third value"); echo "When we use 0,1 as index:

";

代码如下	复制代码
$fruit = array('a' => 'apple', 'b' => 'banana', 'c' => 'cranberry'); reset($fruit); while (list($key, $val) = each($fruit)) {       echo "$key => $valn"; } ?>

$a=each($arr); echo "My position in the $arr array is: ".$a['0']; echo "
"; echo "My value in the $arr array is: ".$a['1']; echo "

"; echo "When we use key and value as index:

"; $b=each($arr); echo "My position in the $arr array is:".$b['key']; echo "
"; echo " My value in the $arr array is: ".$b['value']; ?>

displays as: When we use 0,1 as index: My position in the $arr array is: 0 My value in $arr array is: I am the first value When we use key and value as index: My position in the $arr array is: 1 My value in the $arr array is: I am the second value You can also use the each function combined with the list function to traverse the array, as in the following example: Example 3:

The code is as follows	Copy code
$fruit = array('a' => 'apple', 'b' => 'banana', 'c' => 'cranberry'); reset($fruit); while (list($key, $val) = each($fruit)) { echo "$key => $valn"; } ?>

displays as:

a => apple b => banana c => cranberry

It should be noted here that the subscript of the list function must be a number and must start from 0.

Explanation of reset function inside

:

After executing each(), the array pointer will stay at the next cell in the array or at the last cell when the end of the array is reached. If you want to use each to iterate through the array again, you must use reset(). If it is the first time to traverse the array, you don't need to use it.

Let’s talk about the reset function in detail:

reset is to point the internal pointer of the array to the first unit. The syntax is:

mixed reset (array &$array)

reset() rewinds the internal pointer of array to the first element and returns the value of the first array element, or FALSE if the array is empty.

You can compare the example 2 above with the example below to understand it easily. . . ,

Code:

$b=each($arr); echo "My position in the $arr array is:".$b['key'];

The code is as follows

代码如下	复制代码
$arr=array("我是第一个值","我是第二个值","我是第三个值"); echo "当我们用0,1为索引时： "; $a=each($arr); echo "我在$arr数组中的位置为：".$a['0']; echo " "; echo "     我在$arr数组中的值为：".$a['1']; echo " "; echo "当我们用key,value为索引时： "; reset($arr); $b=each($arr); echo "我在$arr数组中的位置为：".$b['key']; echo " "; echo "     我在$arr数组中的值为：".$b['value']; ?>

Copy code

$arr=array("I am the first value","I am the second value","I am the third value");

echo "When we use 0,1 as index:

";
$a=each($arr);

echo "My position in the $arr array is: ".$a['0'];

echo "
";

echo " My value in the $arr array is: ".$a['1'];

echo "

";
echo "When we use key and value as index:

";

reset($arr);

echo "
"; echo " My value in the $arr array is: ".$b['value'];

?>

displays as: When we use 0,1 as index: My position in the $arr array is: 0 My value in $arr array is: I am the first value When we use key and value as index:

My position in the $arr array is: 0 My value in the $arr array is: I am the first value //Pay attention to the display of this line in Example 2, you will understand

http://www.bkjia.com/PHPjc/631626.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/631626.htmlTechArticleThe article introduces the detailed application of PHP list(), each(), and reset() functions. Friends who need to know more You can refer to it. 1. List function The list function assigns the values ​​in the array to some variables. The syntax is as follows...