Passing Array Using Html Form Hidden Element

May 6, 2007

Html form hidden element is used to pass information which is not visible to the user but used internaly by underlying scripts. For example the status of the process or step of multi step form submission. PHP array is an important language structure used in manipulation of multiple values associated with single object. Sometimes it is required to pass these values accross the pages between browser and the server. Following method can be used to pass PHP Arrays using html form hidden elements.

Using individual array element

This method uses seperate hidden element for each element in array. This can be done by following method.

foreach ($my_array as $key => $value)
{
 echo ‘<input type=hidden name=”my_array[]” value=”‘.htmlspecialchars($value).'”>’;
}

This will generate an array in html form. And when submitted can be accessed by form handling PHP script using following code.
$my_array = $_POST[‘my_array’];

Combining all array elements in one value to hidden element

In this method all elements in an array are combined in single value using implode() PHP function. implode() will return a string combining all the array elements in the same order, seperated by given string. Then this combined value can be passed in html form hidden element. See below.
$single_value = implode(“,”, $my_array);
echo ‘<input type=hidden name=”single_value” value=”‘.htmlspecialchars($single_value).'”>’;

And when submitted the array can be retreived using explode() PHP function. explode() will return an array by spliting the string using the given seperator. See code below.
$my_array = explode(“,”,$_POST[‘single_value’]);

Advertisements

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


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);
?>