EXTRACT a slice of a given ARRAY.
<?php
arr array_slice ( arr $array , int $offset [,
int $length = NULL [, bool $preserve_keys = FALSE ]] )
where,
$array = The input ARRAY
$offset = The position where the sequence will start
( SEE the below TABLE )
$length = The length of the sequence
( SEE the below TABLE )
$preserve_keys = To control the reorder and reset the integer array keys
( SEE the below TABLE )
?>
| VALUE | MEANING |
| $offset > 0 | The sequence will start at that offset in the $array. |
| $offset = 0 | The sequence will start at the beginning of the $array. |
| $offset < 0 | The sequence will start that far from the end of the $array. |
| ed48 | |
| VALUE | MEANING |
| $length = NULL | The sequence will have the length of the $array. |
| $length > 0 | The sequence will have up to that many elements in it. |
| $length < 0 | The sequence will will stop that many elements from the end of the $array. |
| ed48 | |
| VALUE | MEANING |
| FALSE | This function will reorder and reset the integer array indexes. |
| TRUE | This function will not reorder and reset the integer array indexes. |
| ed48 | |
EXERCISE
<?php
$arr01 = [ "HSK" => [ "HUE", "SATURATION", "BLACK" ],
"RGBc" => [ "RED", "GREEN", "BLUE" ],
"RGBt" => [ "[0,255", "[0,255]", "[0,255]" ] ];
echo 'The given $arr01:<br>';
print_r($arr01);
echo '<br><br><br>';
echo 'offset = ';
$offset01 = mt_rand(-4, 4);
echo $offset01 . '<br><br>';
$length01 = NULL;
// DEFAULT
$prskey01 = FALSE;
// DEFAULT
/* - - - - - - - - - - - - - - - - - - - - - - - -
$slc01 = array_slice($arr01,
$offset01,
$length01,
$prskey01);
- - - - - - - - - - - - - - - - - - - - - - - - - - */
$slc01 = array_slice($arr01, $offset01);
echo 'After array_slice($arr01, $offset01):<br>';
print_r($slc01);
?>
EXERCISE
<?php
$arr02 = [ "HSK" => [ "HUE", "SATURATION", "BLACK" ],
"RGBc" => [ "RED", "GREEN", "BLUE" ],
"RGBt" => [ "[0,255", "[0,255]", "[0,255]" ] ];
echo 'The given $arr02:<br>';
print_r($arr02);
echo '<br><br><br>';
echo 'offset = ';
$offset02 = mt_rand(-4, 4);
echo $offset02 . '<br><br>';
echo 'length = ';
$length02 = mt_rand(-4, 4);
echo $length02 . '<br><br>';
echo 'preserve_keys = ';
$prskey02 = TRUE;
var_dump($prskey02);
echo '<br><br>';
$slc02 = array_slice($arr02,
$offset02,
$length02,
$prskey02);
echo 'After array_slice($arr01,
$offset01,
$length02,
$prskey02):<br>';
print_r($slc02);
?>
EXERCISE
<?php
$arr03 = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
echo 'The given $arr03<br>';
print_r($arr03);
echo '<br><br><br>';
echo 'offset = ';
$offset03 = mt_rand(-5, 5);
echo $offset03 . '<br><br>';
echo 'length = ';
$length03 = mt_rand(-45, 45);
echo $length03 . '<br><br>';
$prk03 = mt_rand(0, 1);
if($prk03 == 0)
{
$prskey03 = FALSE;
}
else
{
$prskey03 = TRUE;
}
echo 'preserve_keys = ';
var_dump($prskey03);
echo '<br><br>';
$slc03 = array_slice($arr03,
$offset03,
$length03,
$prskey03);
echo 'After array_slice($arr03,
$offset03,
$length03,
$prskey03):<br>';
print_r($slc03);
?>
EXERCISE
<?php
$arr04d = array("Chastity",
"Generosity",
"Temperance",
"Diligence",
"Patience",
"Charity",
"Humility");
echo 'The given $arr04d:<br>';
var_dump($arr04d);
echo '<br><br><br>';
echo 'offset = ';
$offset04d = 1;
// Deprecating Chastity!!!!!!
echo $offset04d . '<br><br>';
echo 'length = ';
$lngt04d = mt_rand(1, 6);
// Random choice of 1 to 6 remaining virtues
echo $lngt04d . '<br><br>';
echo 'preserve_keys = ';
$prsrv04d = false;
// Undoing parity between indexes and elements
var_dump($prsrv04d);
echo '<br><br>';
$slc04d = array_slice($arr04d,
$offset04d,
$lngt04d,
$prsrv04d);
echo 'After array_slice($arr04d,
$offset04d,
$lngt04d,
$prsrv04d):<br>';
var_dump($slc04d);
?>
EXERCISE
<?php
$var_array =
array(
array(),
array(1,2,3,4,5,6,7,8,9),
array("One", "Two",
"Three",
"Four",
"Five"),
array(6, "six", 7, "seven",
8, "eight",
9, "nine"),
array( "a" => "aaa", "A" => "AAA",
"c" => "ccc",
"d" => "ddd",
"e" => "eee"),
array("1" => "one", "2" => "two",
"3" => "three",
"4" => "four",
"5" => "five"),
array(1 => "one", 2 => "two",
3 => 7,
4 => "four",
5 => "five"),
array("f" => "fff", "1" => "one",
"" => "blank",
2.4 => "float",
"F" => "FFF",
"blank" => "", 3.7 => 3.7,
5.4 => 7,
6 => 8.6,
'5' => "Five"),
array(12, "name", 'age', '45'),
array( array("oNe", "tWo", 4),
array(10, 20, 30, 40, 50),
array())
);
echo 'The given $var_array;<br>';
var_dump($var_array);
echo '<br><br><br>';
$num = 4;
$str = "john";
$counter = 1;
foreach ($var_array as $sub_array)
{
/* variations with two arguments */
/* offset values >, < and = 0 */
echo"<br><br><u>Iteration: ".$counter."</u><br>";
echo"Variation with first two Arguments:<br>";
var_dump ( array_slice($sub_array, 1) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2) );
/* variations with three arguments */
/* offset value variations with length values */
echo"<br><br><br>Variation with first three Arguments:<br>";
var_dump ( array_slice($sub_array, 1, 3) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 1, 0) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 1, -3) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0, 3) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0, 0) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0, -3) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2, 3) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2, 0 ) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2, -3) );
/* variations with four arguments */
/* offset value, length value
and preserve_key values variation */
echo"<br><br><br>Variation with first two arguments
with preserve_key value TRUE:<br>";
var_dump ( array_slice($sub_array, 1, 3, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 1, 0, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 1, -3, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0, 3, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0, 0, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, 0, -3, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2, 3, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2, 0, true) );
echo '<br><br>';
var_dump ( array_slice($sub_array, -2, -3, true) );
$counter++;
}
/* variation of offset
and length to point to same element */
echo"<br><br><br>Typical Variation of offset
and length Arguments:<br>";
var_dump (array_slice($var_array[2], 1, -3, true) );
echo '<br><br>';
var_dump (array_slice($var_array[2], 1, -3, false) );
echo '<br><br>';
var_dump (array_slice($var_array[2], -3, -2, true) );
echo '<br><br>';
var_dump (array_slice($var_array[2], -3, -2, false) );
?>
EXERCISE
<?php
/*
* Pass different integers
* as $offset argument
* to test how array_slice() behaves
*/
echo "Testing array_slice() : usage variations.";
$input = array ('one' => 1,
2 => 'two',
'three',
9 => 'nine',
'ten' => 10);
echo '<br><br>The given $input:<br>';
var_dump($input);
echo '<br><br>';
for ($i = -7; $i <= 7; $i++) {
echo "<br><br>\$offset is $i:<br>";
var_dump(array_slice($input, $i));
}
echo "<br><br><br>\$offset is maximum integer value:<br>";
var_dump(array_slice($input, PHP_INT_MAX));
echo "<br><br><br>\$offset is minimum integer value:<br>";
var_dump(array_slice($input, -PHP_INT_MAX));
?>
EXERCISE
<?php
/*
* Pass different integer values
* as $length argument to
* array_slice() to test behaviour
*/
echo "Testing array_slice() : usage variations.";
$input = array ('one' => 1,
2 => 'two',
'three',
9 => 'nine',
'ten' => 10);
echo '<br><br>The given $input:<br>';
var_dump($input);
$offset = 1;
echo "<br><br>Offset: $offset";
for ($i = -6; $i <= 6; $i++) {
echo "<br><br>\$length is $i:<br>";
var_dump(array_slice($input, $offset, $i));
}
echo "<br><br><br>\$length is maximum integer value:<br>";
var_dump(array_slice($input, $offset, PHP_INT_MAX));
echo "<br><br><br>\$length is minimum integer value:<br>";
var_dump(array_slice($input, $offset, -PHP_INT_MAX));
?>
EXERCISE
<?php
/*
* Pass different data types as keys
* in an array to array_slice()
* to test how $preserve_keys treats them
*/
echo "Testing array_slice() : usage variations.";
// Initialise function arguments not being substituted
$offset = 0;
$length = 10; // to ensure all elements are displayed
//get an unset variable
$unset_var = 10;
unset ($unset_var);
// heredoc string
$heredoc = <<<EOT
hello world
EOT;
// arrays of different data types to be passed as $input
$inputs = array(
// int data
/*1*/ 'int' => array(
0 => 'zero',
1 => 'one',
12345 => 'positive',
-2345 => 'negative',
),
// float data
/*2*/ 'float' => array(
10.5 => 'positive',
-10.5 => 'negative',
.5 => 'half',
),
/*3*/ 'extreme floats' => array(
12.3456789000e6 => 'large',
12.3456789000E-10 => 'small',
),
// null data
/*4*/ 'null uppercase' => array(
NULL => 'null 1',
),
/*5*/ 'null lowercase' => array(
null => 'null 2',
),
// boolean data
/*6*/ 'bool lowercase' => array(
true => 'lowert',
false => 'lowerf',
),
/*7*/ 'bool uppercase' => array(
TRUE => 'uppert',
FALSE => 'upperf',
),
// empty data
/*8*/ 'empty double quotes' => array(
"" => 'emptyd',
),
/*9*/ 'empty single quotes' => array(
'' => 'emptys',
),
// string data
/*10*/ 'string' => array(
"stringd" => 'stringd',
'strings' => 'strings',
$heredoc => 'stringh',
),
// undefined data
/*11*/ 'undefined' => array(
@$undefined_var => 'undefined',
),
// unset data
/*12*/ 'unset' => array(
@$unset_var => 'unset',
),
);
// loop through each element of $inputs
// to check the behavior of array_slice()
$iterator = 1;
foreach($inputs as $type => $input) {
echo "<br><br>Iteration $iterator : key type is $type:<br>";
echo "<b>\$preserve_keys = TRUE</b><br>";
var_dump( array_slice($input, $offset, $length, true) );
echo "<br><b>\$preserve_keys = FALSE</b><br>";
var_dump( array_slice($input, $offset, $length, false) );
$iterator++;
};
?>
EXERCISE
<?php
/*
* Test array_slice when passed
* 1. a two-dimensional array as $input argument
* 2. a sub-array as $input argument
*/
echo "Testing array_slice() : usage variations.";
$input = array ('zero', 'one',
array('zero', 'un', 'deux'),
9 => 'nine');
echo 'The given $input:<br>';
var_dump($input);
echo "<br><br>Slice a two-dimensional array:<br>";
var_dump(array_slice($input, 1, 3));
echo "<br><br>\$input is a sub-array:<br>";
var_dump(array_slice($input[2], 1, 2));
?>
EXERCISE
<?php
/*
* Test array_slice() when:
* 1. Passed an array of referenced variables
* 2. $input argument is passed by reference
*/
echo "Testing array_slice() : usage variations.";
$val1 = 'one';
$val2 = 'two';
$val3 = 'three';
echo '<br><br>Array of
referenced variables ($preserve_keys = default):<br>';
$input = array(3 => &$val1, 2 => &$val2, 1 => &$val3);
var_dump(array_slice($input, 1, 2));
echo '<br><br>Change $val2 ($preserve_keys = TRUE):<br>';
$val2 = 'hello, world';
var_dump(array_slice($input, 1, 2, true));
?>
EXERCISE
<?php
/*
* Check position of internal
* array pointer after calling array_slice()
*/
echo "Testing array_slice() : usage variations.";
$input = array ('one' => 'un', '
two' => 'deux',
23 => 'twenty-three',
'zero');
echo 'The given $input:<br>';
var_dump($input);
echo "<br><br>Call array_slice():<br>";
var_dump($result = array_slice($input, 2));
echo "<br><br><br>Position of Internal Pointer in Result:<br>";
echo key($result) . " => " . current($result) . "<br>";
echo "<br>Position of Internal Pointer in Original Array:<br>";
echo key($input) . " => " . current ($input) . "<br>";
?>
EXERCISE
<?php
/*
* Check that results of array_slice
* are correct when there are holes
* in buckets caused by unset()
*/
echo "Testing array_slice() : usage variations.";
function dump_slice(array $input,
$offsetToUnset,
int $offset,
int $length) {
unset($input[$offsetToUnset]);
var_dump(array_slice($input, $offset, $length));
echo '<br><br>';
}
echo "<br><br>Call array_slice()
on array with string keys:<br>";
$input = ['one' => 'un',
'two' => 'deux',
23 => 'twenty-three',
'zero'];
dump_slice($input, 'two', 0, 1);
dump_slice($input, 'two', 0, 2);
dump_slice($input, 'two', 0, 3);
dump_slice($input, 23, 1, 2);
echo "<br>Call array_slice() on array with packed keys:<br>";
$input = [10, 11, 12, 'thirteen'];
dump_slice($input, 0, 0, 1);
dump_slice($input, 1, 0, 1);
dump_slice($input, 1, 0, 3);
dump_slice($input, 1, -1, 1);
dump_slice($input, 1, 0, 3);
dump_slice($input, 1, -3, 3);
?>