You can't go very far with PHP and not come across arrays, or rather PHP's idea of arrays, even its own manual acknowledges that PHP arrays are actually ordered maps. The array type is introduced via PHP: Arrays - Manual and then PHP: Arrays - Manual introduces all of the supporting functions.

It is worth highlighting there are two ways to define an array, as follows:
$myarray = array('key' => 'value');
$myarray = ['key' => 'value'];
Both work equally well.