Use of list () in PHP

List () like array (), this is not the real function, but the language structure . list () assigns a set of variables in one-step operation. Example:

<?php

$a =array (a);

$b =array (' x ', ' y ', ' z ');

List ($b, $a) = $a;

echo $a, ' ~ ~ ~ ', $b;

Analysis: At this point, first $a= $a [1], $b = $a [0],list () is assigned from left to right, the assignment from right to left, so at this point $a=2, $a this time the value of the integer int is stored, so $a[0] is equal to NULL, then $a[0] assignment to $b

Results: 2~~~

?>

<?php

$a =array (' 1 ', ' 2 ', ' 3 ');

$b =array (' x ', ' y ', ' z ');

List ($b, $a) = $a;

echo $a, ' ~ ~ ~ ', $b;

Analysis: At this point, first $a= $a [1], $b = $a [0],list () is assigned from left to right, the assignment from right to left, so at this time $a= ' 2 ', $a this time to store a string type of value, and the string can be considered an indexed array, so $a[0]= ' 2 ', and then the $a [0] assign to $b

Results: 2~~~2

?>

<?php

Exchange values of 2 variables without using the third variable

$a = 3;
$b = 9;
List ($b, $a) =array ($a, $b);
echo $a, ' ~ ~ ', $b;//The result is: 9~~~3

?>

<?php

$arr =array (' 1 ' = ' A ', ' 3 ' = ' B ', ' 2 ' = ' C ');
List ($a,, $c) = $arr;
echo $a, ' ~ ~ ~ ', $c;

Analysis: Assign the corresponding value first, $a = $arr [0], $c = $arr [2], and then assign the value $c=c, $a =null

Results: ~~~c

?>

Use of list () in PHP