Programming PHP

• The empty string ("") and the string "0"
• An array with zero elements
• An object with no values or functions
• The NULL value
Any value that is not false is true, including all resource values (which are described
later, in the “Resources” section).
PHP provides true and false keywords for clarity:
$x = 5; // $x has a true value
$x = true; // clearer way to write it
$y = ""; // $y has a false value
$y = false; // clearer way to write it
Use the is_bool( ) function to test whether a value is a boolean:
if (is_bool($x)) {
// $x is a boolean
}
Arrays
An array holds a group of values, which you can identify by position (a number, with
zero being the first position) or some identifying name (a string):
$person[0] = "Edison";
$person[1] = "Wankel";
$person[2] = "Crapper";
$creator['Light bulb'] = "Edison";
$creator['Rotary Engine'] = "Wankel";
$creator['Toilet'] = "Crapper";
The array( ) construct creates an array:
$person = array('Edison', 'Wankel', 'Crapper');
$creator = array('Light bulb' => 'Edison',
'Rotary Engine' => 'Wankel',
'Toilet' => 'Crapper');
There are several ways to loop across arrays, but the most common is a foreach loop:
foreach ($person as $name) {
echo "Hello, $name\n";
}
foreach ($creator as $invention => $inventor) {
echo "$inventor created the $invention\n";
}
Hello, Edison
Hello, Wankel
Hello, Crapper
Edison created the Light bulb
Wankel created the Rotary Engine
Crapper created the Toilet
This is the Title of the Book, eMatter Edition
Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.
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