PHP Cookies Tutorial And PHP Cookies Examples

March 6, 2007

In the course of developing highly interactive web sites it is necessary to deal with large amount of data flow between client browswer and web server. It is quite cumbersome handling such large amount of data using hidden fiels in HTML forms. This problem can be overcomed by using HTTP cookies. HTTP cookies are the bunch of data/text sent by the server to the web browswer. Web browser store this data locally and send back to the server each time it accesses the server before it expires. Note that now a days Most browsers allow users choice to accept cookies or not, sometime rejection causes web site to not work properly.

setcookie() function.
This function in PHP Language is used to work with HTTP cookies. setcookie() defines a cookie to be sent along with the rest of the HTTP headers. This must be called before sending any output to the browser because cookies are part of the HTTP header. On successful it will return TRUE. But this does not mean that client browser has ccepted cookie.

setcookie() syntax.
bool setcookie ( string name [, string value [, int expire [, string path [, string domain [, int secure]]]]])

  • name: This argument sets the name of the cookie.
    for example setcookie(‘mycookie’, …) will set mycookie and is called $_COOKIE[‘mycookie’] at server side.
  • value: This will set the value of the cookie. Since this values is stored on the client browser extra care must be taken that it does not store some secure information e.g passwords. The values is accessed by $_COOKIE[‘mycookie’] at the web server.
  • expire: Sets the expire time of cookie. It is Unix timestamp so generally it is used with time() function. For example time()+60*30. This will set the cookie to expire in 30 minutes. If not set the cookie is not persistent and will expire when the browser closes.
  • path: The path of cookies are used to organise cookies based on the path at web server. If set to ‘/’ this cookie is availabe to all directories. If set to ‘/dir1/’ this cookie is availabe to dir1 only and all sub directories of /dir1 i.e /dir1/sub1. Note that the default value is the current directory so if the current directory is ‘/dir1/’ and you want to set it for all directories it must be ‘/’
  • domain: This argument will decide in which domain cookie is accesible. Value ‘www.mydomin.com’
    makes it accesible to www sub-domain only. To make it accessible to all subdomains of mydomin.com a value
    ‘.mydomin.com’ must be set.
  • secure: Value 1 indicates the cookie must be used on secure (https) connection. Default value is 0.

setcookie() Examples.
setcookie(‘mycookie’, ‘Test mycookie’); This will set ‘mycookie’ with value ‘Test mycookie’ will expire when browser closes.
setcookie(‘mycookie’, ‘Test mycookie’, time()+3600*24); This will expire in 1 day.
setcookie(‘mycookie’, ‘Test mycookie’, time()+3600*24, “/dir1/”); Available to /dir1 directory and all subdirectories under it.

Accessing cookie values at server.
At server in PHP script, cookies sent from the client browser will be turned into PHP variables. After PHP 4.1.0 the global array variable $_COOKIE is set for cookies from the client. $HTTP_COOKIE_VARS is also present which is availabe before PHP 4.1.0. See example below.
echo $_COOKIE[“mycookie”]; This will output “Test mycookie” in our example.

Testing cookie.
On successful return of setcookie() does not mean that client browser has accepted the cookie or cookie is set successfully. It must be checked on next loading of the page if a cookie was successfully set or not. This can be done by using PHP function print_r($_COOKIE) function. This will show weather the cookie is set or not.

Deleting a cookie.
Cookies can be deleted by setting its value to “” and all other parameters must be the same as they were set at the time of sending the cookie. We must ensure that the expiration date is in the past when deleting the cookie. See examples below.

setcookie (“mycookie”, “”, time() – 3600);
setcookie (“mycookie”, “”, time() – 3600, “/dir1/”);

Multiple cookies.
Multiple cookies can be set using following.
setcookie(‘mycookie1’, ‘Test mycookie1’);
setcookie(‘mycookie2’, ‘Test mycookie2’);
setcookie(‘mycookie3’, ‘Test mycookie3’);
setcookie(‘mycookie4’, ‘Test mycookie4’);

And can be accessed by following.
echo $_COOKIE[“mycookie1”];
echo $_COOKIE[“mycookie2”];
echo $_COOKIE[“mycookie3”];
echo $_COOKIE[“mycookie4”];

Cookies Array.
We can use PHP array in cookies. see example below
setcookie(“mycookie[0]”, “value1”);
setcookie(“mycookie[1]”, “value2”);
setcookie(“mycookie1[‘one’]”, “value11”);
setcookie(“mycookie1[‘five’]”, “value15”);

This is similar of setting many cookies but the values are placed in the PHP array at the
receing PHP script.

foreach ($_COOKIE[‘mycookie’] as $key => $value) {
  echo “$key:$value “;
  }
This will print 0:value1 1:value2
And
foreach ($_COOKIE[‘mycookie1’] as $key => $value) {
  echo “$key:$value “;
  }
Will print print one:value11 five:value15

Advertisements

PHP Arrays Tutorial and PHP Array Examples

February 25, 2007

An array in PHP is actually an ordered map. A map is a type that maps values to keys. This type is optimized in several ways, so you can use it as a real array, or a list (vector), hashtable (which is an implementation of a map), dictionary, collection, stack, queue and probably more. Because you can have another PHP array as a value, you can also quite easily simulate trees.

PHP Array Syntax: Create an Array
language-construct array() is used to create an array in PHP. See example below

array( [key =>] value
  , …
  )
key: key may be an integer or string
value: A value can be of any PHP type

Examples
$arr = array(“foo” => “bar”, 12 => true);
echo $arr[“foo”]; this will print bar
echo $arr[12]; this will print 1

if you provide the brackets with no key specified, then the maximum of the existing integer indices +1 is taken as key. see below

$arr = array(5 => 1, 12 => 2); This will create an array with 2 elements
$arr[] = 56;     new key will be maximum key + 1 i.e $arr[13] = 56
$arr[“x”] = 42;  This adds a new element to the array with key “x”

array(5 => 43, 32, 56, “b” => 12); This array is the same as following.
array(5 => 43, 6 => 32, 7 => 56, “b” => 12);

Handling arrays from html form inputs to php scripts
Following example will show we can use an array from html form inputs.

HTML form with array
<input type=”checkbox” name=”selected_ids[]” value=”1″>
<input type=”checkbox” name=”selected_ids[]” value=”2″>
<input type=”checkbox” name=”selected_ids[]” value=”3″>
<input type=”checkbox” name=”selected_ids[]” value=”11″>
<input type=”checkbox” name=”selected_ids[]” value=”12″>
<input type=”checkbox” name=”selected_ids[]” value=”13″>

When we submit above form, it will generate $_POST[‘selected_ids’][] array to the form handling php script. This array holds all selected checkbox values from above html form. foreach() construct can be used to extract values from the array. Following code example will show how we can extract those values from the returning array.

foreach ($_POST[‘selected_ids’] as $key => $value) {
    echo “Key: $key; Value: $value<br>”;
}
for example if 1,2 and 12 is selected from the above html form then above code will print
Key: 0 Value: 1
Key: 1 Value: 2
Key: 2 Value: 12


Using remote files in PHP

February 17, 2007

As long as allow_url_fopen is enabled in php.ini, you can use HTTP and FTP URLs with most of the functions that take a filename as a parameter. In addition, URLs can be used with the include(), include_once(), require() and require_once() statements. In PHP 4.0.3 and older, in order to use URL wrappers, you were required to configure PHP using the configure option –enable-url-fopen-wrapper.

Getting the title of a remote page
For example, you can use code below to to open a file from a remote web server and extract title of the page.

<?php
$file = fopen (“http://www.example.com/&#8221;, “r”);
if (!$file) {
    echo “<p>Unable to open remote file.\n”;
    exit;
}
while (!feof ($file)) {
    $line = fgets ($file, 1024);
    /* This only works if the title and its tags are on one line */
    if (eregi (“<title>(.*)</title>”, $line, $out)) {
        $title = $out[1];
        break;
    }
}
fclose($file);
?> 

Reading the contents of a remote file
fread function can be used to read content of remote file. This is shown in example below. You should collect the data together in chunks as shown in the example below because reading will stop after a packet is available.

<?php
$handle = fopen(“http://www.example.com/&#8221;, “rb”);
$contents = ”;
while (!feof($handle)) {
  $contents .= fread($handle, 8192);
}
fclose($handle);
?> 

reading the contents of a file into array
file function returns the file in an array. Each element of the array corresponds to a line in the file, with the newline still attached. Each line in the resulting array will include the line ending, so you still need to use rtrim() if you do not want the line ending present.

<?php
// Get a file into an array.  In this example we’ll go through HTTP to get
// the HTML source of a URL.
$lines = file(‘http://www.example.com/&#8217;);

// Loop through our array, show HTML source as HTML source; and line numbers too.
foreach ($lines as $line_num => $line) {
    echo “Line #<b>{$line_num}</b> : ” . htmlspecialchars($line) . “<br />\n”;
}
?>

reading the contents of a file into a string

file_get_contents() returns the file in a string. This is the preferred way to read the contents of a file into a string. It will use memory mapping techniques if supported by your OS to enhance performance.

<?php
$content_string = file_get_contents(‘www.example.com/products.html’);
?>

Storing data on a remote server
You can also write to files on an FTP server (provided that you have connected as a user with the correct access rights). You can only create new files using this method; if you try to overwrite a file that already exists, the fopen() call will fail. You need to specify the username and password within the URL, such as ‘ftp://user:password@ftp.example.com/path/to/file’.

<?php
$file = fopen (“ftp://ftp.example.com/incoming/outputfile”, “w”);
if (!$file) {
    echo “<p>Unable to open remote file for writing.\n”;
    exit;
}
/* Write the data here. */
fwrite ($file, $_SERVER[‘HTTP_USER_AGENT’] . “\n”);
fclose ($file);
?> 


PHP File Upload

February 15, 2007

PHP can be used to receive files from any RFC-1867 compliant browser. This can be used to upload both text and binary files from browsers. See the file upload html form below:

<form enctype=”multipart/form-data” action=”handle_upload.php” method=”post”>
 <input type=”hidden” name=”MAX_FILE_SIZE” value=”30000″>
 Select File: <input name=”myfile” type=”file”>
 <input type=”submit” value=”Upload”>
</form>

  • MAX_FILE_SIZE hidden field restrict the maximum filesize accepted in bytes and must precede the file input field
  • enctype=”multipart/form-data” is used to handle file uploads and file will be uploaded as MIME data streams. Otherwise the file upload will not work.

The Variables, in PHP script which receives file upload, differs depending on the PHP version and configuration. The $_FILES exists as of PHP 4.1.0 The $HTTP_POST_FILES array has existed since PHP 4.0.0. These arrays hold uploaded file information. Using $_FILES is preferred.
The contents of $_FILES from above script is as follows.

  • $_FILES[‘myfile’][‘name’] The original name of the file on the client machine.
  • $_FILES[‘myfile’][‘type’] The mime type of the file, if the browser provided this information. An example would be “image/gif”.
  • $_FILES[‘myfile’][‘size’] The size, in bytes, of the uploaded file.
  • $_FILES[‘myfile’][‘tmp_name’] The temporary filename of the file in which the uploaded file was stored on the server.
  • $_FILES[‘myfile’][‘error’] Since PHP 4.2.0, PHP returns an appropriate following error code along with the file array
    UPLOAD_ERR_OK – Value: 0; There is no error, the file uploaded with success.
    UPLOAD_ERR_INI_SIZE Value: 1; The uploaded file exceeds the upload_max_filesize directive in php.ini.
    UPLOAD_ERR_FORM_SIZE Value: 2; The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.
    UPLOAD_ERR_PARTIAL Value: 3; The uploaded file was only partially uploaded.
    UPLOAD_ERR_NO_FILE Value: 4; No file was uploaded.

Uploaded Files will by default be stored in the server’s default temporary directory. Variable $_FILES[‘myfile’][‘tmp_name’] will hold the info about where it is stored. The move_uploaded_file function needs to be used to store the uploaded file to the correct location. See the code below:

$uploaddir = “uploads/”;
$uploadfile = $uploaddir . basename( $_FILES[‘myfile’][‘name’]);

if(move_uploaded_file($_FILES[‘myfile’][‘tmp_name’], $uploadfile))
{
  echo “The file has been uploaded successfully”;
}
else
{
  echo “There was an error uploading the file”;
}


php connection status and connection handling

January 24, 2007

There are three possible php connection states are maintained Internally. They are NORMAL, ABORTED and TIMEOUT. When the script is running normally the NORMAL php connection state is active. If the connection between client and server is stopped or disconnected it is in ABORTED state. If the max_execution_time of PHP script is expired the TIMEOUT state is active. The max_execution_time value is defined in the php.ini if it is not defined the default value is 30 seconds. There are functions availabe in PHP that can be used to control php connection status.

ignore_user_abort() function By default the php script is aborted when client stops or disconneted. Sometime it is required to always have the scripts run to completion. This function sets whether a client disconnect should cause a script to be aborted. It will return the previous setting and can be called without an argument to not change the current setting and only eturn the current setting. This behaviour can also be set via the ignore_user_abort php.ini directive as well as through the corresponding “php_value ignore_user_abort” Apache .conf directive.

register_shutdown_function() function. By default the php script is aborted when client stops or disconneted. One exception to this is if you have registered a shutdown function using register_shutdown_function(). This registered shutdown function will get called when the script is aborted by client disconnect. Note that this registered shutdown function will get called even if the script is terminating normally. For example such call register_shutdown_function(my_register_function) will register my_register_function() and will get called when underlying php script is terminating. Multiple calls to register_shutdown_function() can be made, and each will be called in the same order as they were registered. If you call exit() within one registered shutdown function, processing will stop completely and no other registered shutdown functions will be called. It is not possible to send any output to the browser in registered shutdown functions because they are called after the request has been completed including sending any output.

connection_aborted() function. This function returns TRUE if client disconnected. Typically this function is useful in registered shutdown functions to do something different in case of a client disconnect and php connection status is ABORTED.

Controling script execution time set_time_limit() function. The default timeout for any php script is 30 seconds. This can be changed using the max_execution_time php.ini directive or the corresponding “php_value max_execution_time” Apache .conf directive. This can also be controled run time by using set_time_limit() function. This function sets the number of seconds a script is allowed to run. If seconds is set to zero, no time limit is imposed. When called, set_time_limit() restarts the timeout counter from zero. i.e if the timeout is the default 30 seconds, and after 25 seconds into script execution a call set_time_limit(20) is made, the script will allow to run for a total of 45 seconds before timing out.

connection_timeout() function. This function returns TRUE if php connection status is TIMEOUT. Typically this function is useful in registered shutdown functions to do something different in case of php connection status is TIMEOUT.

connection_status() function. Note that both the ABORTED and the TIMEOUT states can be active at the same time. This is possible when ignore_user_abort is set and client disconnected. At this time script will keep running but PHP will still note that it is ABORTED. If it then TIMEOUT it will stop execution of the script and registered shutdown function will be called if registered. At this point connection_timeout() and connection_aborted() will return TRUE. connection_status() can also be used which returns the connection status bitfield. So, if both states are active it would return 3.