PHP Programming/Arrays
Arrays are sets of data that can be defined in a PHP Script. Arrays can contain other arrays inside of them without any restriction (hence building multidimensional arrays). Arrays can be referred to as tables or hashes.
Syntax
[edit | edit source]Arrays can be created in two ways. The first involves using the function array. The second involves using square brackets.
The array function method
[edit | edit source]In the array function method, you create an array in the scheme of:
$foo = bar()
For example, to set up the array to make the keys sequential numbers (Example: "0, 1, 2, 3"), you use:
$foobar = array($foo, $bar);
This would produce the array like this:
$foobar[0] = $foo;
$foobar[1] = $bar;
It is also possible to define the key value:
$foobar = array('foo' => $foo, 'bar' => $bar);
This would set the array like this:
$foobar['foo'] = $foo;
$foobar['bar'] = $bar;
The square brackets method
[edit | edit source]The square brackets method allows you to set up by directly setting the values. For example, to make $foobar[1] = $foo
, all you need to do is:
$foobar[1] = $foo;
The same applies for setting the key value:
$foobar['foo'] = $foo;
Examples of arrays
[edit | edit source]Example #1
[edit | edit source]<?php
$array = array("name"=>"Toyota","type"=>"Celica","colour"=>"black","manufactured"=>"1991");
$array2 = array("Toyota","Celica","black","1991");
$array3 = array("name"=>"Toyota","Celica","colour"=>"black","1991");
print_r($array);
print_r($array2);
print_r($array3);
?>
Array ( [name] => Toyota [type] => Celica [colour] => black [manufactured] => 1991 ) Array ( [0] => Toyota [1] => Celica [2] => black [3] => 1991 ) Array ( [name] => Toyota [0] => Celica [colour] => black [1] => 1991 )
Example #2
[edit | edit source]The following example will output the identical text as Example #1:
<?php
$array['name'] = "Toyota";
$array['type'] = "Celica";
$array['colour'] = "black";
$array['manufactured'] = "1991";
$array2[] = "Toyota";
$array2[] = "Celica";
$array2[] = "black";
$array2[] = "1991";
$array3['name'] = "Toyota";
$array3[] = "Celica";
$array3['colour'] = "black";
$array3[] = "1991";
print_r($array);
print_r($array2);
print_r($array3);
?>
Example #3
[edit | edit source]<?php
echo "Manufacturer: {$array['name']} \n";
echo "Brand: <b>{$array2['1']}</b><br />\n";
echo "Colour: <b>".$array3['colour']."</b><br />\n";
echo "Year Manufactured: <b>".$array3[1]."</b><br />\n"
?>
Manufacturer: <b>Toyota</b><br /> Brand: <b>Celica</b><br /> Colour: <b>black</b><br /> Year Manufactured: <b>1991</b><br />
Manufacturer: Toyota Brand: Celica Colour: black Year Manufactured: 1991
Multidimensional arrays
[edit | edit source]Elements in an array can also be an array, allowing for multidimensional arrays. An example, in accordance with the motoring examples above, is:
<?php
$cars = array(
"car1" => array("make" => "Toyota","colour" => "Green","year" => 1999,"engine_cc" => 1998),
"car2" => array("make" => "BMW","colour" => "RED","year" => 2005,"engine_cc" => 2400),
"car3" => array("make" => "Renault","colour" => "White","year" => 1993,"engine_cc" => 1395),
);
?>
In this example, if you were to use:
<?php
echo "$cars['car1']['make']<br>";
echo "$cars['car3']['engine_cc']";
?>
The output would be:
Toyota
1395
Array functions
[edit | edit source]There are dozens of array manipulation functions. Before implementing your own, make sure it doesn't already exist as a PHP function in Array functions (PHP manual entry).
Sorting
[edit | edit source]Examples:
$array = array("name"=>"Toyota", "type"=>"Celica", "colour"=>"black", "manufactured"=>"1991");
array_multisort($array, SORT_ASC);
var_dump($array);
// array(4) { ["manufactured"]=> string(4) "1991" ["type"]=> string(6) "Celica" ["name"]=> string(6) "Toyota" ["colour"]=> string(5) "black" }
// The upper cases are sorted before the lowercases.
arsort($array);
var_dump($array);
// array(4) { ["colour"]=> string(5) "black" ["name"]=> string(6) "Toyota" ["type"]=> string(6) "Celica" ["manufactured"]=> string(4) "1991" }
asort($array);
var_dump($array);
// array(4) { ["manufactured"]=> string(4) "1991" ["type"]=> string(6) "Celica" ["name"]=> string(6) "Toyota" ["colour"]=> string(5) "black" }
sort($array);
var_dump($array);
// array(4) { [0]=> string(4) "1991" [1]=> string(6) "Celica" [2]=> string(6) "Toyota" [3]=> string(5) "black" }
Array traversal
[edit | edit source]In various circumstances, you will need to visit every array element and perform a task upon it.
The simplest and the most widely used method for this is the foreach operator that loops through the whole array and works individually with each key/item couple. If a more complex way of traversing the array is needed, the following functions operate using the internal array pointer:
- reset - sets the internal pointer to the first element and returns the first element
- prev - sets the internal pointer to the previous element and returns it
- current - returns the current element; does not change the internal pointer
- next - sets the internal pointer to the next element and returns it
- each - returns the current element; then sets the internal pointer to the next element
- end - sets the internal pointer to the last element and returns the last element
<?php
// Using an array's iterator to print its values in reverse order
$my_array = array('a', 'b', 'c');
end($my_array);
while ($i = current($my_array)) {
echo $i."\n";
prev($my_array);
}
?>
Another possibility is defining a function and applying it to each array element via one of the following functions:
- array_walk - applies a function to each array element
- array_walk_recursive - same, but if the element is itself an array, it will traverse that array too
External links
[edit | edit source]