A function declaration part will be executed by a call to the function. Programmer has to create Function Calling part inside the respective program.
SYNTAX:
function Name ( );

The index can be assigned automatically in a collection of data set

A multidimensional array is an array containing one or more arrays.

Associative arrays are arrays that use named keys that you assign to them.

array(key= >value,key= >value,key= >value,etc.);
key = Specifies the key (numeric or string value = Specifies the value

Associative arrays are a key-value pair data structure.
Syntax:
array (key⇒ value, key ⇒ value, etc);
key ⇒ Specifies the key (numeric or string)
value ⇒ Specifies the value

There are 3 types of array concepts in PHP.
(i) Indexed Arrays,
(ii) Associative Array and
(iii) Multi-Dimensional Array.

1. The array() function is used to create an array.
2. In PHP,there are three types of arrays:
i). Indexed arrays - Arrays with numeric index
ii). Associative arrays - Arrays with named keys
iii). Multidimensional arrays - Arrays containing one or more arrays

Array is a concept that stores more than one value of same data type in single array variable.

PHP String Functions:
1. trim(): Removes whitespace or other characters from both sides of a string
2. strcmp():Compares two strings (case-sensitive) PHP Array Functions:
3. count():Counts elements in an array, or properties in an object
4. current(): Returns the current element in an array

(i) Values can be passed from one function to another function thru parameters.
(ii) The parameter is also called as arguments, it is like variables.
(iii) The arguments are mentioned after the function name and inside of the parenthesis.

It gives privilege to user to write their own specific operation inside of existing program module is called as User Defined Function.

A function is a type of sub routine or procedure in a program. A function will be executed by a call to the function and the function returns any data type values or NULL. value to the called function in the part of respective program.

Syntax
function functionName([parameter list])
{
// code to be executed
}