PHP Programming/arrays

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Arrays[edit]

Arrays are sets of data which 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]

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]

In the array function method, you create an array in the scheme of:

$foo = bar()

For example, to set the array up 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]

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]

Example #1[edit]

This example sets and prints arrays.

Crystal Clear app terminal.png PHP Code:

<?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);
?>

Crystal Clear app kscreensaver.png PHP Output:

  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
  )

Crystal 128 yast default.png HTML Render:

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]

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]

Using the Example #1 and Example #2 above, now you can try and use arrays the same way as normal variables:

Crystal Clear app terminal.png PHP Code:

<?php
 echo "Manufacturer: &lt;b&gt;{$array['name']}&lt;/b&gt;&lt;br /&gt;\n";
 echo "Brand: &lt;b&gt;{$array2['1']}&lt;/b&gt;&lt;br /&gt;\n";
 echo "Colour: &lt;b&gt;".$array3['colour']."&lt;/b&gt;&lt;br /&gt;\n";
 echo "Year Manufactured: &lt;b&gt;".$array3[1]."&lt;/b&gt;&lt;br /&gt;\n"
?>

Crystal Clear app kscreensaver.png PHP Output:

 Manufacturer: <b>Toyota</b><br />
 Brand: <b>Celica</b><br />
 Colour: <b>black</b><br />
 Year Manufactured: <b>1991</b><br />

Crystal 128 yast default.png HTML Render:

Manufacturer: Toyota
Brand: Celica
Colour: black
Year Manufactured: 1991


Multidimensional Arrays[edit]

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]

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).

Array traversal[edit]

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 which 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]