Archive for the ‘PHP’ Category

PHP count() is O(1)

I was curious about the performance of PHP’s count() function a while back and whether it was worth it to store the result in a variable for repeated use. I discovered the following from this answer by FractalizeR on Stack Overflow:

PHP_FUNCTION(count) calls php_count_recursive(), which in turn calls zend_hash_num_elements() for non-recursive array, which is implemented this way:

ZEND_API int zend_hash_num_elements(const HashTable *ht)
{
IS_CONSISTENT(ht);

return ht->nNumOfElements;
}

So you can see, it’s O(1) for $mode = COUNT_NORMAL.

IMAP Pickup

An interesting little project I wanted to work on; I wanted to be able to pull attachments from emails in an IMAP mailbox and then download them. I wanted an IMAP solution instead of writing a script for the MTA as a script would be specific to the MTA software and not transferable to another server. In addition, there’s also the common case where you may simply not have access to the MTA.

The biggest help in putting this together and dealing with attachments was this blog post and this comment on the PHP docs. Information on doing this is a bit scattered and incomplete in many cases, likely because extracting attachments is somewhat difficult as email is a notoriously bad way to transfer files; the file data is base64 encoded and dumped in as part of the message body.

ImapPickup is the class that encapsulates all the necessary functionality,

class ImapPickup
{
protected $imapStream = null;

protected function findAttachments($part)
{
$partNum = -1;
$attachments = array();

$this->findAttachmentsRec($part, &$attachments, &$partNum, -1);

return $attachments;
}

protected function findAttachmentsRec($part, &$attachments, &$partNum, $partNumSub)
{
if (isset($part->parts))
{
foreach ($part->parts as $partOfPart)
{
$this->findAttachmentsRec($partOfPart, &$attachments, &$partNum, $partNumSub+1);
}
}
else
{

if (isset($part->disposition)){
if ($part->disposition == 'attachment') {
$attachments[] = array($part->dparameters[0]->value, $partNum, $partNumSub);
}
}
}

$partNum++;
}

public function getAttachmentContent($msgNum, $partNum)
{
$contents = imap_fetchbody($this->imapStream, $msgNum, $partNum, FT_UID);
return imap_base64($contents);
}

public function getAttachments($msgNum)
{
$struct = imap_fetchstructure($this->imapStream,$msgNum,FT_UID);
$attachments = $this->findAttachments($struct);

return $attachments;
}

public function getAttachmentsFromMessages($msgArray)
{
$msgIdToAttachmentsMap = array();

if ($msgArray)
{
foreach($msgArray as $msgId)
{
$attachments = $this->getAttachments($msgId);
if(!empty($attachments))
{
$msgIdToAttachmentsMap[$msgId] = $attachments;
}
}
}

return $msgIdToAttachmentsMap;
}

public function getMessages($searchQuery)
{
return imap_search($this->imapStream, $searchQuery, SE_UID);
}

public function connect($mailbox, $user, $password)
{
$this->imapStream = imap_open($mailbox, $user, $password);
}

public function disconnect()
{
imap_close(
$this->imapStream);
}

}

Here’s a little example of how it can be used. This will query all messages with “pickup::” in the subject line and print out the messageID of all messages with attachments, followed by the filenames of all attachments for that message.

$imapPickup = new ImapPickup();
$imapPickup->connect("{mail.hotspotdot.net:143}INBOX", "test@test.net", "pass123");

$messages = $imapPickup->getMessages("SUBJECT pickup::");
$attachments = $imapPickup->getAttachmentsFromMessages($messages);

foreach($attachments as $msgId => $attArr)
{
echo "<p>{$msgId} => ";

foreach($attArr as $attachment)
{
echo $attachment[0];
echo ",";
}

echo "</p>";
}

$imapPickup->disconnect();

The array for a single file attachment contains 3 entries:

  • [0] => filename
  • [1] => major part number
  • [2] => minor part number

getAttachments(), findAttachments(), and findAttachmentsRec() will return an array of such entries (or an empty array is there are no attachments). getAttachmentsFromMessages() will return a map from messageID => array of single attachments.

The part number (both major and minor) is needed to retrieve the contents of an attachment. For getAttachmentContent(), simply use the major number if the minor number is <= 0, or concatenate them with a period separating them (e.g. "2.3").

Unity

I did a little experiment with meshing XML + HTML + PHP.

First, a little background info. Most service-side web technologies (PHP, Ruby on Rails, etc.) were designed around the concept of applying server-side markup to HTML,

<title><?php echo $title;?></title>

… which is interpreted and processed when the page is pulled. There are various frameworks and templating systems to make this easier, cleaner, more structured, etc. but the concept is the same. AJAX comes into play here and there, but it’s seen mostly as a way to sprinkle bits of dynamic data across a page.

This model was fine a few years ago, but for modern web services and apps I think there needs to be a push away from this model, primarily for 2 reasons:

  • Large portions, if not most, of the content of many web apps is dynamic, AJAX-queried data.
  • Support for mobile and desktop platforms connecting to web services is becoming increasingly important; platforms/apps for which HTML/CSS (or at least HTML/CSS designed for a browser) may not serve to provide the best UI.

AJAX structured code fits the bill.

A 100% AJAX architecture elegantly separates application logic (output as XML) from presentation (output as HTML/CSS). Unfortunately, 100% AJAX is not that easy for a complex application. JavaScript interpretation can be slow, killing frontend performance, and backend performance can suffer from the repeated flood of asynchronous requests. In addition, the latency from a multitude of AJAX requests+responses can quickly become noticeable (especially with a burdened backend and during an initial page load). When such issues become apparent, the solution always seems to be to go back to the messy world of hacking server-side tags into HTML.

Unity is an attempt to maintain a 100% AJAX application framework, but alleviate the issues mentioned above for web apps. It’s very, very simple; just a bit of glue that takes the XML from one or more AJAX calls (on localhost; the application server itself), turns it into JSON, and embeds it within the <head> element of the HTML document being served. This should not be done for every call, but for AJAX calls where the data being presented is “mostly static” (e.g. username, messages, etc.). The data can then be accessed in the client-side JavaScript and used as necessary.

Looking at the typical three-tier architecture, Unity is a bit of glue that sits above the app logic (technically, it could be thought of as part of the app logic, but it’s separated here for illustrative purposes).

app stack with glue

However, since the glue makes 1+ calls to fetch the XML from the app logic, things look a bit more like this on the backend:

backend app stack, multiple, with glue

As I mentioned, this is all very simple stuff. Here’s the code that does the magic:

class Unity
{
protected $js = null;
protected $htmlFile = null;

function __construct($_htmlFile)
{
$this->js = array();
$this->js[] = "var Unity = {}";

$this->htmlFile = $_htmlFile;
}

public function PushXml($_xmlFile, $_namespace)
{
$xml = simplexml_load_file($_xmlFile);

// see http://www.php.net/manual/en/function.json-encode.php#97008 for why json_encode is done like this
$this->js[] = "Unity.{$_namespace} = " . json_encode(new SimpleXMLElement($xml->asXML(), LIBXML_NOCDATA));
}

public function PushVar($name, $var)
{
$snippet = "Unity.{$name} = {$var}";
$this->js[] = $snippet;
}

public function UnifyAndEcho()
{
$scriptBlock = implode(';', $this->js);

$dom = new DOMDocument();
$dom->loadHTMLFile($this->htmlFile);
$head = $dom->getElementsByTagName("head")->item(0);

$scriptElem = $dom->createElement('script', $scriptBlock);
$scriptElem->setAttribute("type", "text/javascript");

if($head->firstChild)
{
$head->insertBefore($scriptElem, $head->firstChild);
}
else
{
$head->appendChild($scriptElem);
}

echo $dom->saveHTML();
}
}

Note that you don’t have to parse the XML; json_encode() takes the SimpleXMLElement object and converts the entire tree to JSON. This is done in order to:

  • keep Unity (and the glue layer) as brain-dead simple as possible
  • avoid mucking around with application logic at this level (if the XML doesn’t fits well [e.g. too big, too much unnecessary data, etc.] it’s a problem at a lower level)

Now an example of how the Unity class would be utilized:

$uni = new Unity("test-page.html");
$uni->PushXml("http://localhost/test-xml.xml", "Account");
$uni->UnifyAndEcho();

Assume the XML output is:

<?xml version="1.0" encoding="UTF-8"?>
<root>
<account_info>
<username>
pixel</username>
<stats
timespan="month">
<check_ins>
12432</check_ins>
<photos>
123</photos>
<followers>
32</followers>
</stats>
</account_info>
</root>

… in the client-side JavaScript code, we can access any of this data via Unity.<namespace>… The namespace was specified as “Account”, so the variables can be accessed as follows,

// username
Unity.Account.account_info.username;

// stats.check_ins
Unity.Account.account_info.stats.check_ins;

// ...

Sessions

A not-too-obvious challenge in doing something like this handling session data. As Unity is calling scripts from localhost (and not the client’s computer), a different session, one for localhost, is active. In addition, session data is locked, preventing two active scripts from accessing the same session data (which the xml generating script may very well need)

First, here’s how to get the session id:

session_start();
$sess_id = session_id();
session_write_close();

session_write_close() closes the session so that the subsequent script call will be able to access it. If necessary, session data can be started and access again after or in-between Unity::PushXml() calls; however, again, Unity is meant to be just a lightweight bit of glue, there shouldn’t really be a need to read or manipulate session data at this point in the code.

We can now pass the session id as a GET parameter:

$uni->PushXml($localbase . "controller/getlogin.php?sid={$sess_id}", "Account");

Now within the script being called, session_id() needs to be called with the passed session id, before session_start().

if(isset($_GET['sid']))
{
session_id(
$_GET['sid']);
}

session_start();

That’s it.

Finally it’s worth mentioning that none of this is bound to PHP nor XML. This could be done in any server-side language and the app logic could just as easily output JSON.

PHP session_start() “Node no longer exists”

I stumbled upon this error earlier today as I attempted to store the value of a SimpleXMLElement as a session variable. I was able to narrow down the issue thanks to this post on bytes.com.

According to a user post on the PHP site, this occurs because SimpleXML returns a reference to an object containing the node value, and you can’t store a reference as a session variable. The value must be dereferenced and copied which can be done by casting.

// Bad! $storageBoxSize = $xml->data->storage_box_size;

// Good! $storageBoxSize = (int)$xml->data->storage_box_size;

I find myself hating loosely-typed languages more and more.

PHP Array of MIME Types

Useful for when you need to set HTTP headers when serving file downloads. The mime_content_type function is deprecated and in my case was just returning an empty string. The recommended alternative, using PECL finfo_file, should work fine, but adding and compiling in a PECL extension just for this seems like overkill, especially as you have more control using an array. I’m also never crazy about adding dependencies unless they’re absolutely necessary.

This is from snipplr, but includes the image/png type which was, curiously, missing.

$mime_types = array(
"323" => "text/h323",
"acx" => "application/internet-property-stream",
"ai" => "application/postscript",
"aif" => "audio/x-aiff",
"aifc" => "audio/x-aiff",
"aiff" => "audio/x-aiff",
"asf" => "video/x-ms-asf",
"asr" => "video/x-ms-asf",
"asx" => "video/x-ms-asf",
"au" => "audio/basic",
"avi" => "video/x-msvideo",
"axs" => "application/olescript",
"bas" => "text/plain",
"bcpio" => "application/x-bcpio",
"bin" => "application/octet-stream",
"bmp" => "image/bmp",
"c" => "text/plain",
"cat" => "application/vnd.ms-pkiseccat",
"cdf" => "application/x-cdf",
"cer" => "application/x-x509-ca-cert",
"class" => "application/octet-stream",
"clp" => "application/x-msclip",
"cmx" => "image/x-cmx",
"cod" => "image/cis-cod",
"cpio" => "application/x-cpio",
"crd" => "application/x-mscardfile",
"crl" => "application/pkix-crl",
"crt" => "application/x-x509-ca-cert",
"csh" => "application/x-csh",
"css" => "text/css",
"dcr" => "application/x-director",
"der" => "application/x-x509-ca-cert",
"dir" => "application/x-director",
"dll" => "application/x-msdownload",
"dms" => "application/octet-stream",
"doc" => "application/msword",
"dot" => "application/msword",
"dvi" => "application/x-dvi",
"dxr" => "application/x-director",
"eps" => "application/postscript",
"etx" => "text/x-setext",
"evy" => "application/envoy",
"exe" => "application/octet-stream",
"fif" => "application/fractals",
"flr" => "x-world/x-vrml",
"gif" => "image/gif",
"gtar" => "application/x-gtar",
"gz" => "application/x-gzip",
"h" => "text/plain",
"hdf" => "application/x-hdf",
"hlp" => "application/winhlp",
"hqx" => "application/mac-binhex40",
"hta" => "application/hta",
"htc" => "text/x-component",
"htm" => "text/html",
"html" => "text/html",
"htt" => "text/webviewhtml",
"ico" => "image/x-icon",
"ief" => "image/ief",
"iii" => "application/x-iphone",
"ins" => "application/x-internet-signup",
"isp" => "application/x-internet-signup",
"jfif" => "image/pipeg",
"jpe" => "image/jpeg",
"jpeg" => "image/jpeg",
"jpg" => "image/jpeg",
"js" => "application/x-javascript",
"latex" => "application/x-latex",
"lha" => "application/octet-stream",
"lsf" => "video/x-la-asf",
"lsx" => "video/x-la-asf",
"lzh" => "application/octet-stream",
"m13" => "application/x-msmediaview",
"m14" => "application/x-msmediaview",
"m3u" => "audio/x-mpegurl",
"man" => "application/x-troff-man",
"mdb" => "application/x-msaccess",
"me" => "application/x-troff-me",
"mht" => "message/rfc822",
"mhtml" => "message/rfc822",
"mid" => "audio/mid",
"mny" => "application/x-msmoney",
"mov" => "video/quicktime",
"movie" => "video/x-sgi-movie",
"mp2" => "video/mpeg",
"mp3" => "audio/mpeg",
"mpa" => "video/mpeg",
"mpe" => "video/mpeg",
"mpeg" => "video/mpeg",
"mpg" => "video/mpeg",
"mpp" => "application/vnd.ms-project",
"mpv2" => "video/mpeg",
"ms" => "application/x-troff-ms",
"mvb" => "application/x-msmediaview",
"nws" => "message/rfc822",
"oda" => "application/oda",
"p10" => "application/pkcs10",
"p12" => "application/x-pkcs12",
"p7b" => "application/x-pkcs7-certificates",
"p7c" => "application/x-pkcs7-mime",
"p7m" => "application/x-pkcs7-mime",
"p7r" => "application/x-pkcs7-certreqresp",
"p7s" => "application/x-pkcs7-signature",
"pbm" => "image/x-portable-bitmap",
"pdf" => "application/pdf",
"pfx" => "application/x-pkcs12",
"pgm" => "image/x-portable-graymap",
"pko" => "application/ynd.ms-pkipko",
"pma" => "application/x-perfmon",
"pmc" => "application/x-perfmon",
"pml" => "application/x-perfmon",
"pmr" => "application/x-perfmon",
"pmw" => "application/x-perfmon",
"png" => "image/png",
"pnm" => "image/x-portable-anymap",
"pot" => "application/vnd.ms-powerpoint",
"ppm" => "image/x-portable-pixmap",
"pps" => "application/vnd.ms-powerpoint",
"ppt" => "application/vnd.ms-powerpoint",
"prf" => "application/pics-rules",
"ps" => "application/postscript",
"pub" => "application/x-mspublisher",
"qt" => "video/quicktime",
"ra" => "audio/x-pn-realaudio",
"ram" => "audio/x-pn-realaudio",
"ras" => "image/x-cmu-raster",
"rgb" => "image/x-rgb",
"rmi" => "audio/mid",
"roff" => "application/x-troff",
"rtf" => "application/rtf",
"rtx" => "text/richtext",
"scd" => "application/x-msschedule",
"sct" => "text/scriptlet",
"setpay" => "application/set-payment-initiation",
"setreg" => "application/set-registration-initiation",
"sh" => "application/x-sh",
"shar" => "application/x-shar",
"sit" => "application/x-stuffit",
"snd" => "audio/basic",
"spc" => "application/x-pkcs7-certificates",
"spl" => "application/futuresplash",
"src" => "application/x-wais-source",
"sst" => "application/vnd.ms-pkicertstore",
"stl" => "application/vnd.ms-pkistl",
"stm" => "text/html",
"svg" => "image/svg+xml",
"sv4cpio" => "application/x-sv4cpio",
"sv4crc" => "application/x-sv4crc",
"t" => "application/x-troff",
"tar" => "application/x-tar",
"tcl" => "application/x-tcl",
"tex" => "application/x-tex",
"texi" => "application/x-texinfo",
"texinfo" => "application/x-texinfo",
"tgz" => "application/x-compressed",
"tif" => "image/tiff",
"tiff" => "image/tiff",
"tr" => "application/x-troff",
"trm" => "application/x-msterminal",
"tsv" => "text/tab-separated-values",
"txt" => "text/plain",
"uls" => "text/iuls",
"ustar" => "application/x-ustar",
"vcf" => "text/x-vcard",
"vrml" => "x-world/x-vrml",
"wav" => "audio/x-wav",
"wcm" => "application/vnd.ms-works",
"wdb" => "application/vnd.ms-works",
"wks" => "application/vnd.ms-works",
"wmf" => "application/x-msmetafile",
"wps" => "application/vnd.ms-works",
"wri" => "application/x-mswrite",
"wrl" => "x-world/x-vrml",
"wrz" => "x-world/x-vrml",
"xaf" => "x-world/x-vrml",
"xbm" => "image/x-xbitmap",
"xla" => "application/vnd.ms-excel",
"xlc" => "application/vnd.ms-excel",
"xlm" => "application/vnd.ms-excel",
"xls" => "application/vnd.ms-excel",
"xlt" => "application/vnd.ms-excel",
"xlw" => "application/vnd.ms-excel",
"xof" => "x-world/x-vrml",
"xpm" => "image/x-xpixmap",
"xwd" => "image/x-xwindowdump",
"z" => "application/x-compress",
"zip" => "application/zip" );

Altering the file size limit for PHP uploads

Well, of course, you can edit php.ini to change the file size limit, but for cheap (typically, shared) hosting solutions the issue that pops us is that you don’t have access to it.

I was researching how I could do this w/o modifying php.ini and discovered a forum post that explain a few methods of how it could be done.

Method A (the one that worked for me):
Edit your .htaccess file (if you don’t have one in your web site’s public root directory, you should be able to just create one) and add the following:
php_value post_max_size 8M
php_value upload_max_filesize 8M
(of course, replace 8M with however many megabytes you wish to limit the file sizes of uploads by)

Method B (the one that didn’t work for me):
Use the ini_set function,
ini_set('post_max_size', '8M');
ini_set('upload_max_filesize', '8M');

Method C (the one I didn’t try):
Use a custom php.ini. Not sure exactly what would be involved here, but you’d likely have to programmatically make a copy of the existing php.ini file, modify the copy, and then place the copy in the directory of the script that needs it or in your web site’s public root directory.