From http://www.w3schools.com (Copyright Refsnes Data)

PHP compact() Function

Definition and Usage

The compact() function creates an array from variables and their values.

Syntax

compact(var1,var2...)

Parameter	Description
var1	Required. Can be a string with the variable name, or an array of variables
var2	Optional. Can be a string with the variable name, or an array of variables. Multiple parameters are allowed.

Tips and Notes

Note: Any strings that does not match variable names will be skipped.

Example 1

<?php
$firstname = "Peter";
$lastname = "Griffin";
$age = "38";

$result = compact("firstname", "lastname", "age");

print_r($result);
?>

The output of the code above will be:

Array
(
[firstname] => Peter
[lastname] => Griffin
[age] => 38
)

Example 2

Using a string that does not match a variable, and an array of variable names:

<?php
$firstname = "Peter";
$lastname = "Griffin";
$age = "38";

$name = array("firstname", "lastname");
$result = compact($name, "location", "age");

print_r($result);
?>

The output of the code above will be:

Array
(
[firstname] => Peter
[lastname] => Griffin
[age] => 38
)

Complete PHP Array Reference