php part 2

Select Data From a MySQL Database<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
$conn->close();
?>

<?php
$dbname = "myDB";
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
// output data of each row
while($row = mysqli_fetch_assoc($result)) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
mysqli_close($conn);
?>

PHP Delete Data From MySQL
<?php
$dbname = "myDB";
// Check connection
if (!$conn) {
}
// sql to delete a record
$sql = "DELETE FROM MyGuests WHERE id=3";
if (mysqli_query($conn, $sql)) {
echo "Record deleted successfully";
} else {
echo "Error deleting record: " . mysqli_error($conn);
}
?>

PHP Update Data in MySQL
<?php
$dbname = "myDB";
// Check connection
if (!$conn) {
}
$sql = "UPDATE MyGuests SET lastname='Doe' WHERE id=2";
if (mysqli_query($conn, $sql)) {
echo "Record updated successfully";
} else {
echo "Error updating record: " . mysqli_error($conn);
}
?>

PHP - Validate Name
using RE
$name = test_input($_POST["name"]);
if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
$nameErr = "Only letters and white space allowed";
}
The preg_match() function searches a string for pattern, returning true if the
pattern exists, and false otherwise.

PHP - Keep The Values in The Form
Name: <input type="text" name="name" value="<?php echo $name;?>">
E-mail: <input type="text" name="email" value="<?php echo $email;?>">
Website: <input type="text" name="website" value="<?php echo $website;?>">
Comment: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea>
Gender:
<input type="radio" name="gender"
<?php if (isset($gender) && $gender=="female") echo "checked";?>
value="female">Female
<?php if (isset($gender) && $gender=="male") echo "checked";?>
value="male">Male
<?php if (isset($gender) && $gender=="other") echo "checked";?>
value="other">Other

PHP 5 File Handling
<?php
echo readfile("webdictionary.txt");
?>
The PHP code to read the file and write it to the output buffer is as
follows (the readfile() function returns the number of bytes read on
success

PHP Open File - fopen()
<?php
$myfile = fopen("webdictionary.txt", "r") or die("Unable to open file!");
echo fread($myfile,filesize("webdictionary.txt"));
fclose($myfile);
?>
The first parameter of fread() contains the name of the file to read from
and the second parameter specifies the maximum number of bytes to
read.

Modes Description
r Open a file for read only. File pointer starts at the beginning of the file
w Open a file for write only. Erases the contents of the file or creates a new file if it doesn't exist. File pointer
starts at the beginning of the file
a Open a file for write only. The existing data in file is preserved. File pointer starts at the end of the file.
Creates a new file if the file doesn't exist
x Creates a new file for write only. Returns FALSE and an error if file already exists
r+ Open a file for read/write. File pointer starts at the beginning of the file
w+ Open a file for read/write. Erases the contents of the file or creates a new file if it doesn't exist. File pointer
starts at the beginning of the file
a+ Open a file for read/write. The existing data in file is preserved. File pointer starts at the end of the file.
Creates a new file if the file doesn't exist
x+ Creates a new file for read/write. Returns FALSE and an error if file already exists

PHP 5 File Create/Write
$myfile = fopen("testfile.txt", "w")
The fopen() function is also used to create a file. Maybe a little
confusing, but in PHP, a file is created using the same function used to
open files.
If you use fopen() on a file that does not exist, it will create it, given
that the file is opened for writing (w) or appending (a).

PHP Write to File - fwrite()
<?php
$myfile = fopen("newfile.txt", "w") or die("Unable to open file!");
$txt = "John Doen";
fwrite($myfile, $txt);
$txt = "Jane Doen";
fwrite($myfile, $txt);
fclose($myfile);
?>

PHP 5 Cookies
A cookie is often used to identify a user. A cookie is a small file that the
server embeds on the user's computer. Each time the same computer
requests a page with a browser, it will send the cookie too. With PHP,
you can both create and retrieve cookie values.

PHP Create/Retrieve a Cookie
<?php
$cookie_name = "user";
$cookie_value = "John Doe";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/"); // 86400 = 1 day
?>
<html>
<body>
<?php
if(!isset($_COOKIE[$cookie_name])) {
echo "Cookie named '" . $cookie_name . "' is not set!";
} else {
echo "Cookie '" . $cookie_name . "' is set!<br>";
echo "Value is: " . $_COOKIE[$cookie_name];
}
?>
</body>
</html>
creates a cookie named "user" with the
value "John Doe". The cookie will
expire after 30 days (86400 * 30). The
"/" means that the cookie is available in
entire website (otherwise, select the
directory you prefer).

Delete a Cookie
<?php
// set the expiration date to one hour ago
setcookie("user", "", time() - 3600);
?>
<html>
<body>
<?php
echo "Cookie 'user' is deleted.";
?>
</body>
</html>

What is a PHP Session?
When you work with an application, you open it, do some changes, and then
you close it. This is much like a Session. The computer knows who you are. It
knows when you start the application and when you end. But on the internet
there is one problem: the web server does not know who you are or what
you do, because the HTTP address doesn't maintain state.
Session variables solve this problem by storing user information to be used
across multiple pages (e.g. username, favorite color, etc). By default, session
variables last until the user closes the browser.
So; Session variables hold information about one single user, and are
available to all pages in one application.

Start a PHP Session
<?php
// Start the session
session_start();
?>
<!DOCTYPE html>
<html>
<body>
<?php
// Set session variables
$_SESSION["favcolor"] = "green";
$_SESSION["favanimal"] = "cat";
echo "Session variables are set.";
?>
</body>
</html>

Get PHP Session Variable Values
<?php
session_start();
?>
<!DOCTYPE html>
<html>
<body>
<?php
// Echo session variables that were set on previous page
echo "Favorite color is " . $_SESSION["favcolor"] . ".<br>";
echo "Favorite animal is " . $_SESSION["favanimal"] . ".";
?>
</body>
</html>

Destroy a PHP Session
<?php
session_start();
?>
<!DOCTYPE html>
<html>
<body>
<?php
// remove all session variables
session_unset();
// destroy the session
session_destroy();
?>
</body>
</html>

PHP Exception Handling
Exception handling is used to change the normal flow of
the code execution if a specified error (exceptional)
condition occurs. This condition is called an exception.
This is what normally happens when an exception is
triggered:
• The current code state is saved
• The code execution will switch to a predefined (custom)
exception handler function
• Depending on the situation, the handler may then
resume the execution from the saved code state,
terminate the script execution or continue the script
from a different location in the code

Try, throw and catch
To avoid the error from the example above, we need to create the proper
code to handle an exception.
Proper exception code should include:
• try - A function using an exception should be in a "try" block. If the
exception does not trigger, the code will continue as normal. However if
the exception triggers, an exception is "thrown"
• throw - This is how you trigger an exception. Each "throw" must have at
least one "catch“
• catch - A "catch" block retrieves an exception and creates an object
containing the exception information

<?php
//create function with an exception
function checkNum($number) {
if($number>1) {
throw new Exception("Value must be 1 or
below");
}
return true;
}
//trigger exception in a "try" block
try {
checkNum(2);
//If the exception is thrown, this text will not be
shown
echo 'If you see this, the number is 1 or below';
}
//catch exception
catch(Exception $e) {
echo 'Message: ' .$e->getMessage();
}
?>
The checkNum() function is created. It checks if a number is
greater than 1. If it is, an exception is thrown
The checkNum() function is called in a "try" block
The exception within the checkNum() function is thrown
The "catch" block retrieves the exception and creates an object
($e) containing the exception information
The error message from the exception is echoed by calling $e-
>getMessage() from the exception object

php part 2

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php part 2