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
$file = fopen (“http://www.example.com/”, “r”);
if (!$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/”, “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/’);

// 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”;
}

PHP HTML basic tips and tricks

PHP is an HTML-embedded scripting language. The goal of the language is to allow web developers to write dynamically generated pages quickly. In the course of web development of using PHP PHP and HTML interact a lot. PHP can generate HTML, and HTML can pass information to PHP.

Encoding/decoding when passing a data through a form or URL
Certain characters, for example ‘&’, have special significance in HTML, and should be represented by HTML entities if they are to preserve their meanings. There are several stages for which encoding is important. Assuming that you have a string $data, which contains the string you want to pass on in a non-encoded way, these are the relevant stages.

Passing a value through HTML FORM you must include it in double quotes, and htmlspecialchars() the whole value. For exampe see the code below

<?php echo “<input name=’data’ type=’hidden’ value=’” . htmlspecialchars($data) . “‘>”; ?>

While passing a value through URL you must encode it with urlencode(). It will convert all non-alphanumeric characters except -_. with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs. See example below.
<?php echo “<a href=’” . htmlspecialchars(“/nextpage.php?stage=23&data=” .urlencode($data) . “‘>\n”; ?>

Creating a PHP arrays in a HTML form

To get your FORM result sent as an array to your PHP script you name the INPUT, SELECT, TEXTAREA elements like this:
<input name=”MyArray[]“>
<input name=”MyArray[]“>
<input name=”MyArray[]“>
<input name=”MyArray[]“>

If you do not specify the keys, the array gets filled in the order the elements appear in the form. Above example will contain keys 0, 1, 2 and 3. Notice the square brackets after the variable name, that’s what makes it an array. You can group the elements into different arrays by assigning the same name to different elements:
<input name=”MyArray[]“>
<input name=”MyArray[]“>
<input name=”MyOtherArray[]“>
<input name=”MyOtherArray[]“>
This produces two arrays, MyArray and MyOtherArray, that gets sent to the PHP script. It’s also possible to assign specific keys to your arrays:
<input name=”AnotherArray[]“>
<input name=”AnotherArray[]“>
<input name=”AnotherArray[email]“>
<input name=”AnotherArray[phone]“>
The AnotherArray array will now contain the keys 0, 1, email and phone.

Getting results from a select multiple HTML tag.
The select multiple tag in an HTML construct allows users to select multiple items from a list. These items are then passed to the action handler for the form. The problem is that they are all passed with the same widget name. I.e.
<select name=”var” multiple=”yes”>
Each selected option will arrive at the action handler as var=option1, var=option2, var=option3. Each option will overwrite the contents of the previous $var variable. The solution is to use PHP’s “array from form element” feature. The following should be used:
<select name=”var[]” multiple=”yes”>
Now first item becomes $var[0], the next $var[1], etc.

Passing a variable from Javascript to PHP
Since Javascript is a client-side technology, and PHP is a server-side technology, the two languages cannot directly share variables. It is, however, possible to pass variables between the two. One way of accomplishing this is to generate Javascript code with PHP, and have the browser refresh itself, passing specific variables back to the PHP script. The example below shows precisely how to do this — it allows PHP code to capture screen height and width, something that is normally only possible on the client side.
<?php
if (isset($_GET['width']) AND isset($_GET['height'])) {
  // output the geometry variables
  echo “Screen width is: “. $_GET['width'] .”<br />\n”;
  echo “Screen height is: “. $_GET['height'] .”<br />\n”;
} else {
  // pass the geometry variables
  // (preserve the original query string
  //   — post variables will need to handled differently)

  echo “<script language=’javascript’>\n”;
  echo “  location.href=\”${_SERVER['SCRIPT_NAME']}?${_SERVER['QUERY_STRING']}”
            . “&width=\” + screen.width + \”&height=\” + screen.height;\n”;
  echo “</script>\n”;
  exit();
}
?>