PHP List
PHP Arrays with Security Considerations
Foreword: In this part of the series, I talk about lists in PHP.
By: Chrysanthus Date Published: 7 Nov 2018
Introduction
A List
In PHP, a list is a set of items separated by commas, in square brackets. The items are like elements of an array. Each element can be assigned to a separate variable outside the array. The following is a list of items, which were found on a reading table.
'pen', 'book', 'ruler', 'computer'
If a number is a member of the list, it does not have to be typed in quotes. Any string member has to be typed in quotes. If you want to consider the list as a group, place the list in square brackets, as follows:
['pen', 'book', 'ruler', 'computer']
The following is the creation of an array:
$arr = ['pen', 'book', 'ruler', 'computer'];
The items in a list can be assigned to variables outside the list, using the PHP list() function as follows:
list($var0, $var1, $var2, $var3) = ['pen', 'book', 'ruler', 'computer'];
Try the following code:
<?php
list($var0, $var1, $var2, $var3) = ['pen', 'book', 'ruler', 'computer'];
echo $var0, '<br>';
echo $var1, '<br>';
echo $var2, '<br>';
echo $var3, '<br>';
?>
The output is:
pen
book
ruler
computer
You can still assign the items as follows:
<?php
$arr = ['pen', 'book', 'ruler', 'computer'];
list($var0, $var1, $var2, $var3) = $arr;
echo $var0, '<br>';
echo $var1, '<br>';
echo $var2, '<br>';
echo $var3, '<br>';
?>
If you try this code, the result will be the same as above.
You can decide to copy just the first few items of an array. Try the following code:
<?php
list($var0, $var1) = array('pen', 'book', 'ruler', 'computer');
echo $var0, '<br>';
echo $var1, '<br>';
?>
The output is:
pen
book
If you do not want the function, list(), you can use square brackets on the left hand side of the assignment operator as follows:
<?php
[$var0, $var1] = array('pen', 'book', 'ruler', 'computer');
echo $var0, '<br>';
echo $var1, '<br>';
?>
The output is:
pen
book
Subscripting a List
The subscript for an array element is an integer inside square brackets.
You can subscript a list similar to the way you subscript an array. Try the following code:
<?php
$item = ['pen', 'book', 'ruler', 'computer'][2];
echo $item;
?>
The output is:
ruler
The square brackets with its subscript is just at the end of the list. The expression returns the value whose index is the subscript (index counting begins from zero).
A list can be an associative array. Try the following code:
<?php
$item = ['Pear' => "green", 'Lemon' => "green", 'Apple' => "purple", 'Banana' => "yellow"]['Apple'];
echo $item;
?>
The output is:
purple
, the value of the element whose key is Apple.
That is it for this part of the series. We stop here and continue in the next part.
Chrys
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