Passing Array Using Html Form Hidden Element

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’]);

Using remote files in PHP

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

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”;
}