For newbies like me.

Creating new arrays:-
//Creates a blank array.
$theVariable = array();

//Creates an array with elements.
$theVariable = array("A", "B", "C");

//Creating Associaive array.
$theVariable = array(1 => "http//google.com", 2=> "http://yahoo.com");

//Creating Associaive array with named keys
$theVariable = array("google" => "http//google.com", "yahoo"=> "http://yahoo.com");

Note:
New value can be added to the array as shown below.
$theVariable[] = "D";
$theVariable[] = "E";

To delete an individual array element use the unset function

For example:

<?PHP
    $arr = array( "A", "B", "C" );
    unset( $arr[1] );
    // now $arr = array( "A", "C" );
?>

Unlink is for deleting files.

Converting a linear array (like a mysql record set) into a tree, or multi-dimensional array can be a real bugbear. Capitalizing on references in PHP, we can 'stack' an array in one pass, using one loop, like this:

<?php
# array_stack()
# Original idea from:
# http://www.ideashower.com/our_solutions/
#   create-a-parent-child-array-structure-in-one-pass/
function array_stack (&$a, $p = '@parent', $c = '@children')
{
  $l = $t = array();
  foreach ($a AS $key => $val):
    if (!$val[$p]) $t[$key] =& $l[$key];
    else $l[$val[$p]][$c][$key] =& $l[$key];
    $l[$key] = (array)$l[$key] + $val;
  endforeach;
  return $a = array('tree' => $t, 'leaf' => $l);
}

# Example:
$node = array();
$node[1] = array('@parent' => 0, 'title' => 'I am node 1.');
#     ^-----------------------v Link @parent value to key.
$node[2] = array('@parent' => 1, 'title' => 'I am node 2.');
$node[3] = array('@parent' => 2, 'title' => 'I am node 3.');
$node[4] = array('@parent' => 1, 'title' => 'I am node 4.');
$node[5] = array('@parent' => 4, 'title' => 'I am node 5.');

array_stack($node);

$node['leaf'][1]['title'] = 'I am node one.';
$node['leaf'][2]['title'] = 'I am node two.';
$node['leaf'][3]['title'] = 'I am node three.';
$node['leaf'][4]['title'] = 'I am node four.';
$node['leaf'][5]['title'] = 'I am node five.';

echo '<pre>',print_r($node['tree'],TRUE),'</pre>';
?>

Note that there's no parameter checking on the array value, but this is only to keep the function size small. One could easily a quick check in there to make sure the $a parameter was in fact an array.

Hope you find it useful. Huge thanks to Nate Weiner of IdeaShower.com for providing the original function I built on.

New value can also be added to the array as shown below.
$theVariable["google"] = "http//google.com";
or
$theVariable["1"] = "http//google.com";

If an array item is declared with key as NULL, array key will automatically be converted to empty string '', as follows:

<?php
$a = array(
    NULL => 'zero',
    1    => 'one',
    2    => 'two');

// This will show empty string for key associated with "zero" value
var_dump(array_keys($a));

// Array elements are shown
reset($a);
while( key($a) !== NULL )
{
  echo key($a) . ": ".current($a) . "<br>";// PHP_EOL
  next($a);
}

// Array elements are not shown
reset($a);
while( key($a) != NULL ) // '' == null   => no iteration will be executed
{
  echo key($a) . ": ".current($a) . "<br>";// PHP_EOL
  next($a);
}

Made this function to delete elements in an array;

<?php

function array_del_elm($input_array, $del_indexes) {
    if (is_array($del_indexes)) {
        $indexes = $del_indexes;
    } elseif(is_string($del_indexes)) {
        $indexes = explode($del_indexes, " ");
    } elseif(is_numeric($del_indexes)) {
        $indexes[0] = (integer)$del_indexes;
    } else return;
    $del_indexes = null;
    
    $cur_index = 0;
    if (sort($indexes)) for($i=0; $i<count($input_array); $i++) {
        if ($i == $indexes[$cur_index]) {
            $cur_index++;
            if ($cur_index == count($indexes)) return $output_array;
            continue;
        }
        $output_array[] = $input_array[$i];
    }
    return $output_array;
}

?>

but then i saw the methods of doing the same by Tyler Bannister & Paul, could see that theirs were faster, but had floors regarding deleting multiple elements thus support of several ways of giving parameters. I combined the two methods to this to this:

<?php

function array_del_elm($target_array, $del_indexes) {
    if (is_array($del_indexes)) {
        $indexes = $del_indexes;
    } elseif(is_string($del_indexes)) {
        $indexes = explode($del_indexes, " ");
    } elseif(is_numeric($del_indexes)) {
        $indexes[0] = (integer)$del_indexes;
    } else return;
    unset($del_indexes);
    
    for($i=0; $i<count($indexes); $i++) {
        unset($target_array[$indexes[$i]]);
    }
    return $target_array;
}

?>

Fast, compliant and functional ;)

A small correction to Endel Dreyer's PHP array to javascript array function. I just changed it to show keys correctly:

            function array2js($array,$show_keys)
            {
                $dimensoes = array();
                $valores = array();
               
                $total = count ($array)-1;
                $i=0;
                foreach($array as $key=>$value){
                    if (is_array($value)) {
                        $dimensoes[$i] = array2js($value,$show_keys);
                        if ($show_keys) $dimensoes[$i] = '"'.$key.'":'.$dimensoes[$i];
                    } else {
                        $dimensoes[$i] = '"'.addslashes($value).'"';
                        if ($show_keys) $dimensoes[$i] = '"'.$key.'":'.$dimensoes[$i];
                    }
                    if ($i==0) $dimensoes[$i] = '{'.$dimensoes[$i];
                    if ($i==$total) $dimensoes[$i].= '}';
                    $i++;
                }
                return implode(',',$dimensoes);
            }

Using null as the key when setting an array value is NOT the same as using empty [].
<?php
  $null = null;
  $testArray = [];
  $testArray[$null] = 1;
  $testArray[$null] = 2;
  $testArray[$null] = 3;
  $testArray[$null] = 4;
  var_dump($testArray);
?>
Output:
array(1) {
  '' =>
  int(4)
}

<?php
  $testArray = [];
  $testArray[null] = 1;
  $testArray[null] = 2;
  $testArray[null] = 3;
  $testArray[null] = 4;
  var_dump($testArray);
?>
Output:
array(1) {
  '' =>
  int(4)
}

<?php
  $testArray = [];
  $testArray[] = 1;
  $testArray[] = 2;
  $testArray[] = 3;
  $testArray[] = 4;
  var_dump($testArray);
?>
Output:
array(4) {
  [0] =>
  int(1)
  [1] =>
  int(2)
  [2] =>
  int(3)
  [3] =>
  int(4)
}

Another way to create a multidimensional array that looks a lot cleaner is to use json_decode.  (Note that this probably adds a touch of overhead, but it sure does look nicer.)  You can of course add as many levels and as much formatting as you'd like to the string you then decode.  Don't forget that json requires " around values, not '!!  (So, you can't enclose the json string with " and use ' inside the string.)

As an example:

<?php
    $myarray['blah'] = json_decode('[
        {"label":"foo","name":"baz"},
        {"label":"boop","name":"beep"}
    ]',true);

print_r($myarray)
?>
returns:

Array
(
    [blah] => Array
        (
            [0] => Array
                (
                    [label] => foo
                    [name] => baz
                )
 
            [1] => Array
                (
                    [label] => boop
                    [name] => beep
                )
        )
)