VN4000

PHP - File Upload

noreply@blogger.com (vn4000) — Fri, 05 Jun 2009 23:41:00 +0000

You must first build an HTML form that lets users select a file to upload.

<form enctype="multipart/form-data" action="uploader.php" method="POST">
<input type="hidden" name="MAX_FILE_SIZE" value="100000" />
Choose a file to upload: <input name="uploadedfile" type="file" /><br />
<input type="submit" value="Upload File" />
</form>

enctype="multipart/form-data" - Necessary for our to-be-created PHP file to function properly. The enctype attribute specifies how form-data should be encoded before sending it to the server. See table below.
action="uploader.php" - The name of our PHP page that will be created, shortly.
method="POST" - Informs the browser that we want to send information to the server using POST.
input type="hidden" name="MA... - Sets the maximum allowable file size, in bytes, that can be uploaded.
input name="uploadedfile" - uploadedfile is how we will access the file in our PHP script.

Attribute Values

Value	Description
application/x-www-form-urlencoded	All characters are encoded before sent (this is default)
multipart/form-data	No characters are encoded. This value is required when you are using forms that have a file upload control
text/plain	Spaces are converted to "+" symbols, but no special characters are encoded

Save that form code into a file and call it upload.html.
After the user clicks submit, the data will be posted to the server and the user will be redirected to uploader.php

When the uploader.php file is executed, the uploaded file exists in a temporary storage area on the server. If the file is not moved to a different location it will be destroyed!

Here is uploader.php

$target_path = "uploads/";

$target_path = $target_path . basename( $_FILES['uploadedfile']['name']);

if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) {
echo "The file ". basename( $_FILES['uploadedfile']['name']).
" has been uploaded";
} else{
echo "There was an error uploading the file, please try again!";
}

The $_FILES array is where PHP stores all the information about files.

uploadedfile - uploadedfile is the reference we assigned in our HTML form.
$_FILES['uploadedfile']['name'] - name contains the original path of the user uploaded file.
$_FILES['uploadedfile']['tmp_name'] - tmp_name contains the path to the temporary file that resides on the server. The file should exist on the server in a temporary directory with a temporary name.

PHP - File Append

noreply@blogger.com (vn4000) — Fri, 05 Jun 2009 22:50:00 +0000

If we want to add on to a file we need to open it up in append mode.

$myFile = "testFile.txt";
$fh = fopen($myFile, 'a');

Then we use fwrite() to write to the file. It would begin writing data at the end of the file.

$myFile = "testFile.txt";
$fh = fopen($myFile, 'a') or die("can't open file");
$stringData = "Hello\n";
fwrite($fh, $stringData);
$stringData = "We are vn4000\n";
fwrite($fh, $stringData);
fclose($fh);

PHP - File Delete

noreply@blogger.com (vn4000) — Fri, 05 Jun 2009 22:32:00 +0000

We use unlink() to delete existing files

Before you can delete a file, you must first be sure that it is not open in your program. Use the fclose function to close down an open file.

$myFile = "testFile.txt";
$fh = fopen($myFile, 'w') or die("can't open file");
fclose($fh);
$myFile = "testFile.txt";
unlink($myFile);

PHP - File Read

noreply@blogger.com (vn4000) — Fri, 05 Jun 2009 00:58:00 +0000

The fgets() functions is used to read a line from a file. Using this function we either read the entire line into a string or specify the number characters we like to read.

fgets ($handle, $length);

$handle - the file pointer
$length - number of bytes to read. If length is not specified it will read at the end of the line.

Reading entire line

<?php
$fh = fopen("myfile.txt", "r");

$line = fgets($fh);
echo $line;

fclose($fh);
?>

Reading number of bytes

<?php
$fh = fopen("myfile.txt", "r");

$str = fgets($fh, 64);
echo $str;

$line2 = fgets($fh, 64);
echo $str;

fclose($fh);
?>

Reading file line by line

<?php
$fh = fopen("myfile.txt", "r");

while(true)
{
$line = fgets($fh);
if($line == null)break;

echo $line;
}

fclose($fh);
?>

Reading entire file at once

<?php
$fh = fopen("myfile.txt", "r");

$file = file_get_contents("myfile.txt");
echo $file;
?>

PHP - File Write

noreply@blogger.com (vn4000) — Fri, 05 Jun 2009 00:09:00 +0000

We can easily write text to files using the fwrite() function. However, you must make sure to open file in writable mode before writing.

$myFile = "testFile.txt";
$fh = fopen($myFile, 'w') or die("can't open file");
$stringData = "Hello\n";
fwrite($fh, $stringData);
$stringData = "Welcome to vn4000\n";
fwrite($fh, $stringData);
fclose($fh);

PHP - File Close

noreply@blogger.com (vn4000) — Thu, 04 Jun 2009 22:21:00 +0000

The fclose() function is used to close an open file:

<?php
$file = fopen("test.txt","r");

//some code to be executed

fclose($file);
?>

After a file has been closed down with fclose it is impossible to read, write or append to that file unless it is once more opened up with the fopen function.

PHP - File Open

noreply@blogger.com (vn4000) — Thu, 04 Jun 2009 22:01:00 +0000

We also use fopen() to open existing files as well.

The function fopen() takes in two arguments, the filename and the mode to either open or create a file.

$filename - the name of the file. This may also include the absolute path where you want to create the file. Example, "/www/myapp/myfile.txt".
$mode - mode is used to specify how you want to create the file. For example, you can set the mode to create for read only, or create a file for read and write. Below is the list of possible modes you can use.

PHP file fopen create modes

'w'	Open for writing only; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, it attempt to create it.
'w+'	Open for reading and writing; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.
'a'	Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
'a+'	Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it.

There are additional ways to open a file.

Read/Write: 'r+'

Opens a file so that it can be read from and written to. The file pointer is at the beginning of the file.

Write/Read: 'w+'

This is exactly the same as r+, except that it deletes all information in the file when the file is opened.

Append: 'a+'

This is exactly the same as r+, except that the file pointer is at the end of the file.

PHP - File Create

noreply@blogger.com (vn4000) — Thu, 04 Jun 2009 21:31:00 +0000

Using the PHP file system function fopen(), we can create a new file

The function fopen() takes in two arguments, the filename and the mode to either open or create a file.

$filename - the name of the file. This may also include the absolute path where you want to create the file. Example, "/www/myapp/myfile.txt".
$mode - mode is used to specify how you want to create the file. For example, you can set the mode to create for read only, or create a file for read and write.

Example:

$ourFileName = "testFile.txt";
$ourFileHandle = fopen($ourFileName, 'w') or die("can't open file");
fclose($ourFileHandle);

$ourFileName = "testFile.txt";
The name of our file is "testFile.txt" and it is stored into a String variable $ourFileName.
$ourFileHandle = fopen($ourFileName, 'w') or die("can't open file");
We use the function fopen and give it two arguments: our file name and we inform PHP that we want to write by passing the character "w".
fclose($ourFileHandle);
We close the file that was opened. fclose takes the file handle that is to be closed.

PHP Post and Get

noreply@blogger.com (vn4000) — Thu, 04 Jun 2009 21:04:00 +0000

Both the GET and POST methods send data to the server.

The POST method was intended to create a resource. The contents of the resource would be encoded into the body of the HTTP request.

The GET method is different in that it passes the variables along to the PHP web page by appending them onto the end of the URL

Use the POST method if any of the following are true:

The result of the request has persistent side effects such as adding a new database row.
If the data collected on the form is likely to result in a large URL if implemented using the GET method.
The data to be sent is in any encoding other than seven-bit ASCII.

Use the GET method if all the following are true:

If the request is essentially finding a resource, and HTML
form data is to help that search.
The result of the request has no persistent side effects.
If the data collected and the input field names in a HTML
are less than 1,024 characters in length.

PHP - Do while

noreply@blogger.com (vn4000) — Thu, 04 Jun 2009 20:50:00 +0000

A do-while loop checks the test condition (the condition that is defined inside the while) at the end of the loop. Regular while loops check the test condition at the beginning of the loop.

PHP While loop

<?php
$i = 0;
while($i > 0){
echo $i;
}
?>

As you can see, this while loop's conditional statement failed ($i is not greater than 0), which means the code within the while loop was not executed

PHP Do While loop

<?php
$i = 0;
do {
echo $i;
} while ($i > 0);
?>

The above loop would run one time exactly, since after the first iteration, when truth expression is checked, it evaluates to FALSE ($i is not bigger than 0) and the loop execution ends.

PHP - For each

noreply@blogger.com (vn4000) — Wed, 03 Jun 2009 17:18:00 +0000

PHP provides an easy way to use every element of an array with the Foreach statement.

Example

$employeeAges;
$employeeAges["Hoang"] = "28";
$employeeAges["Thao"] = "19";
$employeeAges["Tuan"] = "25";
$employeeAges["Mai"] = "26";
$employeeAges["Hoa"] = "32";

foreach( $employeeAges as $key => $value){
echo "Name: $key, Age: $value
";
}

$something as $key => $value

The operator "=>" represents the relationship between a key and value. Example, we only changed the variable names that refer to the keys and values

$employeeAges;
$employeeAges["Hoang"] = "28";
$employeeAges["Thao"] = "19";
$employeeAges["Tuan"] = "25";
$employeeAges["Mai"] = "26";
$employeeAges["Hoa"] = "32";

foreach( $employeeAges as $name=> $age){
echo "Name: $name, Age: $age
";
}

PHP - For Loop

noreply@blogger.com (vn4000) — Wed, 03 Jun 2009 17:04:00 +0000

The common tasks that are covered by a for loop are:

Set a counter variable to some initial value.
Check to see if the conditional statement is true.
Execute the code within the loop.
Increment a counter at the end of each iteration through the loop.

The basic structure of the for loop:

for ( initialize a counter; conditional statement; increment a counter){
do this code;
}

For loop has three statements.

In the first statement, we initialize a counter variable to an number value.
In the second statement, we set a condition (a max/min number value) until the counter is reached.
In the third statement, we set a value by how much we want the counter variable to incremented by.

Example:

<?php

for($i=0; $i<=5; $i=$i+1)
{
echo $i." ";
}

?>

Will Print number through 0 to 5

PHP -While Loop

noreply@blogger.com (vn4000) — Wed, 03 Jun 2009 00:14:00 +0000

Here is the basic structure of a PHP while loop:

while ( conditional statement is true){
 //do this code;
}

Example - Print number through 1 to 5 with PHP While Loop
<?php

$i = 1;
while ($i <= 5 )
{
echo $i . "<br>";

$i = $i + 1;
}

?>

PHP - Array

noreply@blogger.com (vn4000) — Wed, 03 Jun 2009 00:06:00 +0000

An array is a data structure that stores one or more values in a single value.

Structure of an array

$employee_array[0] = "Hung";
$employee_array[1] = "Thao";
$employee_array[2] = "Thang";
$employee_array[3] = "Hoa";

The general form for setting the key of an array equal to a value is:

$array[key] = value;

Note: As you may have noticed from the above code example, an array's keys start from 0 and not 1.

Display content:

echo "Two of my employees are "
. $employee_array[0] . " & " . $employee_array[1]; 
echo "
Two more employees of mine are " 
. $employee_array[2] . " & " . $employee_array[3];

PHP - Functions

noreply@blogger.com (vn4000) — Tue, 02 Jun 2009 18:05:00 +0000

A function is just a name we give to a block of code that can be executed whenever we need it. When you create a function, you first need to give it a name, like myFunction.

Create Function

<?php
function myFunction(){
echo "Hello, We are vn4000!<br />";
}
?>

Using your Function

<?php
function myFunction(){
echo "We are vn4000!";
}
echo "Welcome to our homepage. ";
myCompanyMotto();
?>

Function Parameters

<?php

function myGreeting($name){

echo "Hello there ". $firstName . "!<br />";

}

myGreeting("vn4000");

?>

Function returning Values

<?php
function mySum($numX, $numY){
$total = $numX + $numY;
return $total;
}
$myNumber = 0;
echo "Before the function, myNumber = ". $myNumber ."<br />";
$myNumber = mySum(3, 4); // Store the result of mySum in $myNumber
echo "After the function, myNumber = " . $myNumber ."<br />";
?>

PHP - Switch Statement

noreply@blogger.com (vn4000) — Tue, 02 Jun 2009 14:38:00 +0000

With the use of the switch statement you can check for all these conditions at once. The way the Switch statement works is it takes a single variable as input and then checks it against all the different cases you set up for that switch statement.

Example

<?php
switch ($y)
{
case 1:
echo "y equals to 1";
break;
case 2:
echo "y equals to 2";
break;
case 3:
echo "y equals to 3";
break;
default:
echo "y is not equals to 1, 2 or 3";
}
?>

PHP - If...Else

noreply@blogger.com (vn4000) — Tue, 02 Jun 2009 00:20:00 +0000

Example:

<?php
$the_number = 4000;

if ( $the_number == 4000 ) {
echo "The if statement evaluated to true";
} else {
echo "The if statement evaluated to false";
}
?>

* We first made a PHP variable called $the_number and set it equal to 4000.
* In this example we compared a variable to an integer value. To do such a comparison we use "==", which in English means "Is Equal To".
* $the_number is indeed Equal To 4000 and so this statement will evaluate to true.
* All code that is contained between the opening curly brace "{" that follows the if statement and the closing curly brace "}" will be executed when the if statement is true.
* The code contained within the else segment will not used.

PHP - If Statement

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 20:02:00 +0000

Example

<?php
$my_name = "vn4000";

if ( $my_name == "vn4000" ) {
echo "Your name is vn4000!<br />";
}
echo "Welcome to my homepage!";
?>

We first set the variable $my_name equal to "vn4000".
We next used a PHP if statement to check if the value contained in the variable $my_name was equal to "vn4000"
The comparison between $my_name and "vn4000" was done with a double equal sign "==", not a single equals"="! A single equals is for assigning a value to a variable, while a double equals is for checking if things are equal.
Translated into english the PHP statement ( $my_name == "vn4000" ) is ( $my_name is equal to "vn4000" ).
$my_name is indeed equal to "vn4000" so the echo statement is executed.

PHP - Include File

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 18:42:00 +0000

The PHP include command takes a file name and simply inserts that file's contents into the script that issued the include command.

Example

link.php

<html>
<body>
<a href="http://www.vn4000.com/index.php">vn4000</a>

index.php

<?php include("link.php"); ?>
<p>Hello World!</p>
</body>
</html>

PHP - Comments

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 18:35:00 +0000

Single Line Comment

<?php
echo "Hello World!"; // This will print out Hello World!
?>

Multiple Line Comment

<?php
echo "Hello World!";
/* echo "My name is vn4000!";
echo "We are
PHP Programmers!";
*/
?>

Display:

Hello World!

PHP - Operators

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 18:18:00 +0000

There are 5 categories of operators in PHP

Assignment Operators
Arithmetic Operators
Comparison Operators
String Operators
Combination Arithmetic & Assignment Operators

Assignment operators are used to set a variable equal to a value or set a variable to another variable's value.

Example:

$my_var = vn4000;

Arithmetic Operators

Operator	English	Example
+	Addition	2 + 4
-	Subtraction	6 - 2
*	Multiplication	5 * 3
/	Division	15 / 3
%	Modulus	43 % 10

Comparison Operators

Comparisons are used to check the relationship between variables and/or values.

Operator	English	Example	Result
==	Equal To	$x == $y	false
!=	Not Equal To	$x != $y	true
<	Less Than	$x < $y	true
>	Greater Than	$x > $y	false
<=	Less Than or Equal To	$x <= $y	true
>=	Greater Than or Equal To	$x >= $y	false

String Operators

The period "." is used to add two strings together. Example

<?php
$a_string = "Hello";
$another_string = " vn4000";
$new_string = $a_string . $another_string;
echo $new_string . "!";
?>

PHP - Strings

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 17:38:00 +0000

String

A string variable is used to store and manipulate text.
The string, like a variable, will have to be created first. There are two ways to use a string in PHP – you can store it in a function or in a variable. In the example below, we will create a string twice – the first time storing it in a variable, and the second time – in a function, in our case – an echo.

<?php
$myString = "This is a string!";
echo "This is a string!";
echo $myString;
?>

Display:

This is a string!This is a string!

Single quotes and Double quotes.

There are two ways of quoting when you can specify a string in PHP – single quotes or double quotes.

Example for Single quotes

<?php
$my_string = 'Hello vn4000';
echo 'Hello vn4000';
echo $my_string;
?>

Example for double quotes

<?php
$my_string = "Hello vn4000";
echo "Hello vn4000";
echo $my_string;
?>

The two methods above are the traditional way to create strings in most programming languages. PHP introduces a more robust string creation tool called heredoc that lets the programmer create multi-line strings without using quotations.

Example

<?php
$my_string = <<<TEXT
My
favorite
language
is
PHP
TEXT;
echo $my_string;
?>

PHP- Echo

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 17:31:00 +0000

To output a string,we use PHP echo
Example:

<?php
$myString = "Hello everybody!";
echo $myString;
echo "<b>I am learning PHP!</b>";
?>

Display:

Hello everybody!
I am learning PHP!

PHP - Variables

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 17:27:00 +0000

In PHP you define a variable with the following form:

$variable_name = Value;

If you forget that dollar sign at the beginning, it will not work. This is a common mistake for new PHP programmers!

Here is a example:

<?php
$hello = "Hello vn4000!";
$a_number = 400;
?>

PHP Syntax

noreply@blogger.com (vn4000) — Mon, 01 Jun 2009 17:20:00 +0000

All PHP code must be contained within the following:

<?php

?>

or the Shorthand PHP Tag that requires shorthand support to be enabled on your server

<?

the shorthand PHP tag

?>