PHP

The Zend_Cache class is part of the Zend Framework and is used (as its name suggests) to cache things. This can be anything from the front end browser output to the outcome of a complex calculation or even the results of database queries. Zend_Cache is an enormous topic, not just how the class works, but what the best practices are for caching.

The best place to start with caching is one of the simpler topics of caching database queries, from this point you can work on understanding other caching functionality. Normally, a call to a database table in Zend Framework might be done like this.

I talked a while ago about Adding Code To Wordpress Blogs And Comments, but I decided that it needed a bit of code to do this automatically.

So here it is, prepared by the text processor.

There are three available cryptographic functions in PHP, these are md5(), sha1() and crc32(). All of the functions take a string and output a value that is encrypted and can't be reversed to the original string. In fact the only way to get the original string back is to run a brute force algorithm which tries to guess what the original string was.

To test these functions I will use the following string.

$string = 'wibble';

md5()

This function returns the hash as a 32-character hexadecimal number. The md5() function is used quite a bit and most PHP programmers will have come across it at some point.

Use the following code to create an array of counties in the UK.

The following function will rename all of the image files in a directory to be sequential. The parameters are the path of the directory that the files are in and the name of a function that will be used to sort the array of files through the PHP usort() function.

function sequentialImages($path, $sort=false) {
 $i = 1;
 $files = glob($path."/{*.gif,*.jpg,*.jpeg,*.png}",GLOB_BRACE|GLOB_NOSORT);
 
 if ( $sort !== false ) {
  usort($files, $sort);
 }
 
 $count = count($files);
 foreach ( $files as $file ) {
  $newname = str_pad($i, strlen($count)+1, '0', STR_PAD_LEFT);
  $ext = substr(strrchr($file, '.'), 1);
  $newname = $path.'/'.$newname.'.'.$ext;
  if ( $file != $newname ) {
   rename($file, $newname);  
  }
  $i++;
 }
}

The following function can be used in the second parameter to sort the files by their last modified time.

Use the following function if you want to print the text in a particular colour, depending on what the background colour is.

function opposite($color) {
  $white = 0;
  for ($i = 0; $i < 6; $i += 2) {
    $white += base_convert(substr($color,$i,2),16,10) < 127 ? 1 : 0;
  }
  return $white <= 2 ? "000000" : "ffffff";
}

It works by looking at the colour and seeing how much of it is white. If greater than two parts are significantly white then the color returned is black, otherwise white is returned.

Here are some examples to test the function out.

This simple code example uses a combination of strrchr to find the last occurrence of a string and substr to return part of the string in order to find the file extension for a given filename. This is ideal if you want to quickly find a file extension.

$ext = substr(strrchr($fileName, '.'), 1);

This code can be used in the following way.

$fileName = '\path\to\file\afile.wibble';
$ext = substr(strrchr($fileName, '.'), 1);
echo $ext;

The output here is 'wibble';

Zend_Lucene is an implementation of the Lucene search engine in PHP5 and is included as part of the Zend Framework from version 1.6. Lucene implements all of the standard search engine query syntaxes (eg. boolean and wildcard searches) and stores its index as files so it doesn't need a database server to run. Lucene can be used if you want to add search functionality to a site but don't want to go down the route of building a querying syntax from scratch.

To get started with Lucene you need to create an index. The following code has the effect of creating a directory on your server that Lucene will use to store and retrieve documents.

$index = Zend_Search_Lucene::create('/data/my-index');

To open the index use the following code.

The first thing you learn about in PHP is probably how to print something. This is usually done with a call to the echo or print, but there is another way to print things by writing content directly to the output buffer. The following code looks like you are writing to a file, but the text will appear in the browser window because we are writing to the php://output output stream.

$fp = fopen("php://output", 'r+');
fputs($fp, "Hello World");

Or another way...

file_put_contents("php://output", "Hello World");

The php://output stream is an encapsulation between PHP and the browser. The stream doesn't really exist, but PHP knows what to do with it.

Going back to basics can be useful, even for the most experienced developers. Different languages act and respond in different ways and knowing exactly how some control structures work can be very useful in the long run.

I remember when coding in VB (some years ago now) and realizing that an if statement didn't work like I had expected it to work. I had expected that as soon as a condition was met the code would execute whatever was in that condition and drop out of the if statement. What was actually happening was that the code for any condition met was being executed. I'm not sure if VB still works like that, but it made me realize that a developer must know these things or they could write a system crippling bug without even realizing it.

PHP if statements have been written with efficiency in mind. If a condition is met then the code in the condition is run and the rest of the if statement is skipped. Take the following simple example: