<?php

echo 'Hello World';

?>

unset() sets a variable to “undefined” while unlink() deletes a file we pass to it from the file system.

count() function is used to return the number of elements in an array.

PHP 5 presents many additional OOP (Object Oriented Programming) features.

PEAR means "PHP Extension and Application Repository". It extends PHP and provides a higher level of programming for web developers.

php script.php

finalis introduced in PHP5. Final class means that this class cannot be extended and a final method cannot be overridden.

If we would like to pass values through a form or an URL, then we need to encode and to decode them using htmlspecialchars() and urlencode().

GD library is needed to execute image functions.

To be able to display a human-readable result we use print_r().

The functions are getimagesize() for size, imagesx() for width and imagesy() for height.

imagetypes() gives the image format and types supported by the current version of GD-PHP.

The result set can be handled using mysqli_fetch_array, mysqli_fetch_assoc, mysqli_fetch_object or mysqli_fetch_row.

The function mysqli_num_rows() returns the number of rows in a result set.

mysqli_affected_rows() return the number of entries affected by an SQL query.

It is possible to use the dedicated function, is_numeric() to check whether it is a number or not.

It is possible to use the dedicated function, ctype_alnum to check whether it is an alphanumeric value or not.

If we want to check whether a variable has a value or not, it is possible to use the empty() function.