How to declare and use indexed arrays in PHP.

In PHP, an indexed array is a type of array that contains numerical keys, which can be declared and used in the following way:

Declare an index array.

$array = array("apple", "banana", "cherry", "date");

Using an index array:

echo $array[0]; // 输出：apple
echo $array[1]; // 输出：banana
echo $array[2]; // 输出：cherry
echo $array[3]; // 输出：date

You can use a loop to iterate through elements in an index array.

foreach ($array as $value) {
  echo $value . "<br>";
}

You can also use a for loop to access elements in an indexed array.

for ($i = 0; $i < count($array); $i++) {
  echo $array[$i] . "<br>";
}

You can use the array_push() function to add new elements to an indexed array.

array_push($array, "grape");

You can use the unset() function to remove elements from an indexed array.

unset($array[2]);

Note: The keys of indexed arrays start with 0 and increment by integers, allowing you to access the values of array elements by their index.