PHP

The imagecreatefromjpeg() function has been part of the PHP library since version 4, allowing programmers to load an image directly from a file. However, the imagefilter() has only been available since version 5 and adds a nice little set of effects to an already useful function.

The effects are created using the function in conjunction with a set of constants. Take the following image taken from the free stock images site.

I chose this images because it has lots of colour and will show the techniques working well. To create the effects you need to use the following bit of code, in this case I am using the negative filter.

If you are debugging a PHP application then you might want more information than the values of some current variables. There are a number of built in magic variables that can be used to print out the file name, line number, class and method that the debug statement is printed out on. Here is an example that prints out some information from a class.

One thing that PHP doesn't allow is the creation of multiple functions with the same name. If you try this then PHP will give you a fatal error. Creating different functions with the same name is useful if you want to pass different parameters to a function that produces the same result. There are two ways around this problem.

The first is that you can pass the function an array of the items that you want. You can then use this array in the function to do whatever you want. For example.

I have been doing a lot of benchmarking lately with regards to what is the most efficient way to program PHP. PHP Benchmark is a site that is dedicated to that single task.

This site is in the early stages but looks very promising and deals with some of the major assumptions that programmers have about PHP, including the single and double quotes issue. I would say that most of the tests are only run a few times (around 1000) and so this doesn't give a full representative picture, but I look forward to seeing more from this site in the future.

Here are some links to my own benchmarking tests on #! code

The contents of phpinfo() are quite useful, and it is usually the first thing that many developers perform to make sure that PHP is installed. However, printing out the phpinfo() function can lead to a security risk because it displays a lot of information about the server.

Here is how to write the contents of the phpinfo() function to a file.

ob_start();
phpinfo();
$info = ob_get_contents();
ob_end_clean();
 
$fp = fopen("phpinfo.html", "w+");
fwrite($fp, $info);
fclose($fp);

This is an example of output buffering.

There are many ways to find a string within another string using PHP, but which one is the quickest? I did the same sort of test that I have done with double or single quotes and downloading web pages with a few of the string matching functions available in PHP.

I first generated a very long string that could be used in the string matching functions. The following for loop generates a string containing "iteration 0 and iteration 1 and iteration 2..." right up until "iteration 4999 and".

$testString = '';
for ($i=0; $i < 5000; $i++) {
 $testString .= "iteration " . $i . " and ";
}

This was then passed to a number of string matching functions. This included the regular expression libraries contained in ereg() and preg_match(). The strpos() and strstr() functions were used as these are another common way of string matching, as well as some of their variants for matching case insensitive strings.

Including files in any PHP program is a very common practice and is nothing out of the ordinary. However, problems can occur when a user navigates to a script file that has a function, but is meant to be included as part of the larger program. For example, if your system includes a file to delete something then if that file is run by itself then there is a chance that it will delete everything.

Of course there are other factors like database access, global variables and sessions that would cause any script to simply error and not cause a problem. However, it is good practice to make sure that any include file is only run when it is included, and not when it is run on it's own.

The following little snipped of code can be placed at the top of any include files to make sure that it can't be run outside of an include. The file in this example would be called "test.php".

There are lots of different ways to download a web page using PHP, but which is the fastest? In this post I will go through as many different methods of downloading a web page and test them to see which is the quickest.

Here is a list of the different methods.

• The PHP curl library.
• Snoopy the PHP web browser. Bascially a wrapper for fsockopen.
• fsockopen().
• fopen() with feof().
• fopen() with stream_get_contents().
• file() and then implode().
• file_get_contents() function.

Each method will be run and will retrieve the contents of a web page 50 times each in order to get a decent spread of times. On each run the time will be recorded into an array, this array will then be used at the end to calculate some statistics.

If you have an object or array that you want to save until a later you can use the serialize() and unserialize() functions. The operation of the functions are straightforward. To serialize() an array just pass the serialise function the array like this.

$array = array(1,2,3,4);
$serializedArray = serialize($array);

Now when we print the serialized array out we get the following.

a:4:{i:0;i:1;i:1;i:2;i:2;i:3;i:3;i:4;}

This contains all of the data needed to recreate our array. Be careful not to edit this string because it will not work if you want to unserialize it and get the array back. You can store this string in a file or a database so that you can recreate the exact same array at a later date.