Arrays

An array is a variable that can hold more than one value. Arrays in PHP are stored as value pairs that in other languages would be called a dictionary or a hashtable. Keys can be strings or integers.

Syntax

There are several methods of declaring an array in PHP. The array() function can be used, either with key-value pairs, or with values alone. Single brackets, [...] can also be used in place of the array() keyword. If any key value is omitted, the key will be found by incrementing the largest prior integer key. If a key is repeated, the new value will overwrite the prior key.

<?php
// The last comma can be omitted
$array1 = array( "item 1" => "one", "item 2" => "two", "item 3" => "three", );

echo $array1["item 1"], ";", $array1["item 2"], ";", $array1["item 3"];
// Output: one;two;three

$array2 = array("one", "two", "three");

echo $array2[0], ";", $array2[1], ";", $array2[2];
// Output: one;two;three

$array3 = ["one", 5 => "two", "three"];

echo $array3[0], ";", $array3[5], ";", $array3[6];
// Output: one;two;three

$array4 = [5 => "one", 5.7 => "two", "5" => "three"];

echo $array4[5];
// Output: three
?>

Additionally, when defining an array, the following key casts will occur:

• Strings containing valid int types, unless preceded by a + sign, will be cast to an int type key. As in the above example "5" is treated as 5.
• float types will be cast to int types, truncating the fractional part. As in the above example 5.7 is treated as 5.
• bool types are cast to int types. true is stored as 1 and false stored as 0.
• null will be cast as the empty string, "".
• Arrays and objects cannot be used as keys and will result in an error: Illegal offset type.