'final' is introduced in PHP5. Final class means that this class cannot be extended and a final method cannot be overridden.
How is the comparison of objects done in PHP?
We use the operator '==' to test is two objects are instanced from the same class and have same attributes and equal values. We can test if two objects are referring to the same instance of the same class by the use of the identity operator '==='.
What do the initials of PHP stand for?
PHP means PHP: Hypertext Preprocessor.
Which programming language does PHP resemble?
PHP syntax resembles Perl and C
What does PEAR stand for?
PEAR means "PHP Extension and Application Repository". It extends PHP and provides a higher level of programming for web developers.
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What is the actually used PHP version?
Version 7.1 or 7.2 is the recommended version of PHP.
What Happens If An Expected Input Field Was Not Submitted?
Obviously, if an expected input field was not submitted, there will no entry in the $_REQUEST array for that field. You may get an execution error, if you are not checking the existence of the expected entries in $_REQUEST. For example, if you copy processing_forms.php to your local Web server, and run your browser with http://localhost/processing_forms.php?name=Joe, you will an error page like this:
You have submitted the following information:
Name = Joe
Comments =
Thank you!
PHP Notice: Undefined index:
comment in ...\processing_forms.php on line 3
How To Avoid The Undefined Index Error?
If you don't want your PHP page to give out errors as shown in the previous exercise, you should consider checking all expected input fields in $_REQUEST with the isset() function as shown in the example script below:
<?php
if (isset($_REQUEST['name'])) {
$name = $_REQUEST['name'];
} else {
$name = "";
}
if (isset($_REQUEST['comment'])) {
$comment = $_REQUEST['comment'];
} else {
$comment = "";
}
print("<html><pre>");
print("You have submitted the following information:\n");
print(" Name = $name\n");
print(" Comments = $comment\n");
print("Thank you!\n");
print("</pre></html>\n");
?>
How To List All Values Of Submitted Fields?
If you want list all values of submitted fields, you can write a simple loop to retrieve all entries in the $_REQUEST array. Below is an improved version of processing_forms.php to list all submited input values:
<?php
print("<html><pre>");
$count = count($_REQUEST);
print("Number of values: $count\n");
foreach ($_REQUEST as $key=>$value) {
print(" $key = $value\n");
}
print("</pre></html>\n");
?>
How To Retrieve The Original Query String?
If you have coded some values in the URL without using the standard form GET format, you need to retrieve those values in the original query string in $_SERVER['QUERY_STRING']. The script below is an enhanced version of processing_forms.php which print the original query string:
<?php
print("<html><pre>");
print(" query_string = {$_SERVER['QUERY_STRING']}\n");
$count = count($_REQUEST);
print("Number of values: $count\n");
foreach ($_REQUEST as $key=>$value) {
if (is_array($value)) {
print(" $key is an array\n");
for ($i = 0; $i < count($value); $i++) {
$sub_value = $value[$i];
if (get_magic_quotes_gpc()) {
$sub_value = stripslashes($sub_value);
}
print(" ".$key."[".$i."] = ".$sub_value."\n");
}
} else {
if (get_magic_quotes_gpc()) {
$value = stripslashes($value);
}
print(" $key = $value\n");
}
}
print("</pre></html>\n");
?>
How To Support Multiple-page Forms?
If you have a long form with a lots of fields, you may want to divide the fields into multiple groups and present multiple pages with one group of fields on one page. This makes the a long form more user-friendly. However, this requires you to write good scripts that:
• When processing the first page and other middle pages, you must keep those input values collected so far in the session or as hidden values in the next page form.
• When processing the last page, you should collect all input values from all pages for final process, like saving everything to the database.
How To Close A Session Properly?
Let's say you site requires users to login. When a logged in user clicks the logout button, you need to close the session associated with this user properly in 3 steps:
1. Remove all session values with $_SESSION = array().
2. Remove the session ID cookie with the setcookie() function.
3. Destroy the session object with the session_destroy() function.
Below is a good sample script:
<?php
session_start();
$_SESSION = array();
if (isset($_COOKIE[session_name()])) {
setcookie(session_name(), '', time()-42000, '/');
}
session_destroy();
print("<html><pre>");
print("Thank you for visiting PICKZYCenter.com.\n");
print(" <a href=login.php>Login Again.</a>\n");
print("</pre></html>\n");
?>
How do you execute a PHP script from the command line?
Just use the PHP command line interface (CLI) and specify the file name of the script to be executed as follows:
php script.php
How can PHP and HTML interact?
It is possible to generate HTML through PHP scripts, and it is possible to pass pieces of information from HTML to PHP.
What type of operation is needed when passing values through a form or an URL?
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().
How can we check the value of a given variable is a number?
It is possible to use the dedicated function, is_numeric() to check whether it is a number or not.
How can we check the value of a given variable is alphanumeric?
It is possible to use the dedicated function, ctype_alnum to check whether it is an alphanumeric value or not.
How do I check if a given variable is empty?
If we want to check whether a variable has a value or not, it is possible to use the empty() function.
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