Updating sites—PHP Notes

As I mentioned in the previous posts, I’m using W3Schools to review HTML, CSS, and PHP in order to create some exercises. Here are a few things that I didn’t know about PHP or want to remind myself about.

When sending users to specific pages I often use numbers to indicate which page they should go to. Spambots will frequently put in random junk so I do some tests before I process the request. PHP has some odd behaviour with some of the functions. For example,

// Invalid calculation will return a NaN value
$x = acos(8);
echo is_nan($x);     --> 1
echo var_dump($x);   --> float(NAN)
echo is_null($x);    --> expect 0 but get a blank line, so only works on numbers—not NAN
echo is_finite($x);  --> blank line, so only works on numbers—not NAN

echo is_finite("Hello");     --> Warning: is_finite() expects parameter to be a float
echo is_finite(10);          --> 1
echo is_infinite(10);        --> expect 0 but get a blank line
echo is_infinite(10e1111);   --> 1

// $hello not defined
echo var_dump($hello);       --> NULL
echo is_nan($hello);         --> blank line
echo is_null($hello);        --> 1
echo is_finite($hello);      --> 1
echo is_infinite($hello);    --> expect 0 but get a blank line
echo is_int($hello);         --> expect 0 but get a blank line

var_dump(is_numeric($hello)); --> bool(true) 
is_numeric($hello);           --> expect 0 but get a blank line

I never gave constants much thought when developing web pages, but i’m thinking that they might come in handy when making interactive games. If I access the database and grab a bunch of data that will be displayed but won’t change, it should go into a constant array which is then accessible to any function on the page. Note that both constant arrays and variables are referenced by their name without a $ before the name.

define("cars", [
    "Alfa Romeo",
echo cars[0];  --> Alfa Romeo

function arrayDisplay() {
  foreach (cars as $value) {
        echo "$value ";
arrayDisplay();  --> Alfa Romeo BMW Toyota

If you use a variable array, the array isn’t available to functions.

$cars = array(
    "Alfa Romeo",
var_dump($cars);  -->  array(3) { [0]=> string(10) "Alfa Romeo" [1]=> string(3) "BMW" [2]=> string(6) "Toyota" }

function arrayDisplay() {
  foreach ($cars as $value) {
        echo "$value ";
arrayDisplay(); -- > Warning: Invalid argument supplied for foreach() … 

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