PHP 5 Power Programming

2.8. Functions

A function in PHP can be built-in or user-defined; however, they are both called the same way.

The general form of a function call is

func(arg1,arg2,...)

The number of arguments varies from one function to another. Each argument can be any valid expression, including other function calls.

Here is a simple example of a predefined function:

$length = strlen("John");

strlen is a standard PHP function that returns the length of a string. Therefore, $length is assigned the length of the string "John": four.

Here's an example of a function call being used as a function argument:

$length = strlen(strlen("John"));

You probably already guessed the result of this example. First, the inner strlen("John") is executed, which results in ...