1. A function is created already by system.
2. It is reusable piece or block of code that perform a specific action.
3. Functions can either return values when called or can simply perform an operation without returning any value.
4. Built-in functions are functions that exist in PHP installation package.
5. Functions can either return values when called or can simply perform an operation without returning any value.
Example:
rename_function (): This function renames original name to new name.

Array is a concept that stores more than one value of same data type in single array variable.
They are 3 types of array concepts in PHP.
(i) Indexed Arrays,
(ii) Associative Array and
(iii) Multi-Dimensional Array.
Usage of Array:
When combined with foreach statement which allows loop through an array quickly with very little code.

To pass any number of parameters inside a function.
They are specified inside the parenthesis, after the function name.
Syntax:
function School Name($sname, $Strength)
{
echo $sname." in Tamilnadu and Student Strength is".$Strength;
}

1. PHP has more than 700 built-in functions that perform different tasks.
2. It exists in PHP installation package.
3. It is reusable piece
4. It can either return values when called or can simply perform an operation without returning any value.