PHP

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Last update:   29-10-2021

Arrays

Convertion

PHP automaticaly converts an unitialized array.
 
$x[] = 0;
$x['aa'] = 11;

var_dump($x); // array(2) { [0]=> int(0) ["aa"]=> int(11) } 
Echo don't display value type, and can't be used with arrays and object.
 
$x = 1;
echo $x; // output 1

var_dump($x); // output int(1)

Keys

You can add an element to an array without specifying a key. PHP assigns a number > the greatest key.
 
$a = array (2 => 5);

$a[] = 'a';  // This will have a key of 3
This is true even if the array contains a mix of numerical and string keys.
 
$a = array ('4' => 5, 'a' => 'b');

$a[] = 44; // This will have a key of 5
Array keys are case-sensitive, but type insensitive.
 
$a = array (
    'A' => 1,
    'a' => 2,
    '1' => 3,
    1 => 4,
    '01' => 5, // Only '1' is eq with 1
);

var_dump($a); // [A=>1, a=>2, 1=>3, 01=>5]

List

List constructor assign array's values to individual variables.
 
list($surname, $name, $age) = 

    ["John", "Smith", "34", "07288333"];

echo "$surname $name is $age years old"; 

    // Ouput: John Smith is 34 years old
List is very usefull for string explode.
 
$date = '25/05/2012';
list($day, $month, $year) = explode('/', $date);

echo $month; // 05

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