Php - Array (Map)

About

In Php, an array is an (ordered|sorted) map (keys/value)

Array can contain others arrays.

Element Structure

(Key|Index)

The key can either be an integer or a string (in the same array - PHP does not distinguish between indexed and associative arrays. ).

While automatically indexing occurs, php will start with the integer 0 and add an increment of 1.

'bar' is a string, while bar is an undefined constant. PHP automatically converts a bar string (an unquoted string which does not correspond to any known symbol) into a string which contains the bar string.

Beware that for other data type, the key will be casted Ie a float of 1.5 will be casted to 1).

Value

The value can be of any type.

Because the value of an array can be anything, it can also be another array. This enables the creation of recursive and multi-dimensional arrays.

// Create a new multi-dimensional array
$juices["apple"]["green"] = "good"; 

Length

sizeof($array)

Offset

offset is not a property but is used by function such as array_splice

To retrieve the offset from a key, search the array of key

$offset = array_search($key, array_keys($myArray), true);

Management

Initialization

If multiple elements in the array declaration use the same key, only the last one will be used as all others are overwritten.

Empty

// Before 5.4
$myArray = array();

// As of PHP 5.4
$myArray = []; -- empty array, inside the square brackets, you have an expression. $arr[somefunc($bar)] will work

Non Empty

$array = [
    "key" => "value",
    "foo" => "bar",
    "bar" => "foo",
];
//or
$array = array (
    "key" => "value",
    "foo" => "bar",
    "bar" => "foo",
);

Assignment

Array assignment always involves value copying. (ie not by reference).

$myArray[] = "null";  // assign the next index automatically (ie 0)
$myArray[1] = "one";
$myArray[] = "two"; // assign the next index automatically (ie the last one + 1)
$myArray[3] = "three";

At the beginning

array_unshift($array, "first", "second");

At the end

$myArray[] = "end"; // assign the next index automatically (ie the last one + 1)

Key / Value Existence (In Operator | Contains )

if array_key_exists('key', $myarray) {
    echo "The 'key' element is in the array";
}
  • in_array — Checks if a value exists in an array
if in_array('value', $myarray) {
    echo "'value' is in the array";
}
  • in_array — Checks if a object exists in an array
if in_array($object, $myarray, TRUE) {
    echo "'object' is in the array";
}

Remove

Remove one element by index

  • unset:
    • preserve the internal pointer position
    • does not rearrange the key sequence
unset($myArray[0]); 
$myArray[0] == null
    • does not preserve the internal pointer position (the pointer is reset to the begining)
    • rearrange the key sequence (from 0,1,2)
array_splice ( $array , 0 , 1 ,  [] );
$myArray[0] == "value of second element"

Remove one element by value

if (($key = array_search($valueToDelete, $array)) !== false) {
    unset($array[$key]);
}

Remove the whole array

unset($myArray); 
  • a value
if (($key = array_search($value, $array)) !== false) {
    unset($array[$key]);
}

(List|Print)

  • To the console
var_dump($array);
print_r($array); // Echo Human readable information
  • In a variable (Retrieve the information in a variable, ie Return the output instead of printing it)
arrayInfo = print_r($array,true); 
  • Json
$json = json_encode($_REQUEST)

Reindex

Reindexed using the array_values() function

Slice

array_slice

array_slice ( array $array , int $offset [, int $length = NULL [, bool $preserve_keys = FALSE ]] ) : array

Loop

For / While

List

See list

// My
list($var1, $var2, $var3, $var4) = $myArrayOf4Variables;


// From the doc
$info = array('coffee', 'brown', 'caffeine');
list($drink, $color, $power) = $info;
echo "$drink is $color and $power makes it special.\n";

Functional Programming

Count

count($array);

Replace

Insert

array_splice

array_splice( $original, 3, 0, $inserted );

insert into $origin at index 3, deleting 0, inserting the array $inserted

Append

  • Append one element at the end
$input[] = $x;
  • append two elements at the end
array_push($input, $x, $y);
  • append two elements at the beginning
array_unshift($queue, "0", "1");
  • append an array at the end
array_splice($input, count($input), 0, array($x, $y));
  • array_merge: Only if the arrays contain numeric keys: the value will not overwrite the original value, but will be appended.
$result = array_merge($array1, $array2);

Compare

It is possible to compare arrays with the array_diff() function and with array operators.

Sorting

Arrays are ordered. The order can be changed using various sorting functions.

<?php
sort($files);
print_r($files);
?>

Copy

Array assignment always involves value copying. Use the reference operator to copy an array by reference.

$a =& $b; -- =& is the reference operator

$a and $b point to the same variable space.

Join (to String)

$array = array('lastname', 'email', 'phone');
$comma_separated = implode(",", $array);
echo $comma_separated; // lastname,email,phone

Sort

Sort by value

Ordinal Data - Sorting (Problem / Algorithm) an array in php in ascendant

// if the array contains number
usort($myArray, function($a, $b) {
    return $b - $a; // $a - $b descendant
});

// if the value contains array and that you want to sort on a key
usort($myArray, function($a, $b) {
    return $b['key'] - $a['key'];
});

Sort by key

  • ksort - Sort an array by key
  • asort - Sort an array and maintain index association

Merge / Union

array-merge

$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);

Documentation / Reference


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