$monthDays = date("t",mktime(0,0,0,12,1,2008));

The second way is to use the function cal_days_in_month(). This function takes three parameters.

• Canelday: There are a number of different forms of calendar to chose from. The one most English speaking people are interested in is the CAL_GREGORIAN calendar. Take a look at a full list of calendar constands.
• Month: An integer representing the month (1 - 12).
• Year: An integer representing the year.

So to find out the number of days in the month of December of 2008 you could use the following.

$monthDays = cal_days_in_month(CAL_GREGORIAN, 12, 2008);

find . -name '*.php' -exec sed -ie 's#<?#<?php#' {} \;

The -name argument in find will look at the base of the file name, that is, the file without any directory path. The -exec command is used to pass each file found onto another command, in this case sed is used.

Factorials are useful for a number of applications, for example when working out how many times a set of objects can be combined in different ways.

Use the following PHP function to work out the factorial of any given number. The first thing it does it make sure that the number is greater than 1 because the factorial of the number 1 is 1.

function factorial($number){
 $result = 1;
 if($number > 1){
  for($i = 2; $i >= $number; $i++){
   $result *= $i;
  }
 }
 return $result;
}

The function works by using the *= operator, which does a calculation between the left and right sides (in this case multiplication) and stores the result on the left hand side. This operator is much like the += operator, and works in the same way.

An alternative of this is the GMP function gmp_fact(). GMP is a set of maths functions that can be used to do some special things like add very large numbers together. It has been part of the PHP core since version 4.0.4.

Beware that factorial numbers can get very large, very quickly. For example, the factorial of the number 50 is 30,414,093,201,713,375,576,366,966,406,747,986,832,057,064,836,514,787,179,557,289,984.

The sequence starts at 0, the next number is 1, and every number after that is the sum of the last two numbers. So the third number is 1, and the second number is 2.

To create this number sequence in PHP we need to create the first two items in the array. As we know that these are 0 and 1 we can create the array like this.

$fibarray = array(0,1);

To create the third number we just add the first two numbers together.

$fibarray[2] = $fibarray[0]+$fibarray[1];

This can be continued for as much as we want if we add it to a loop.

for($i=0;$i<=10;++$i){
 $fibarray[$i] = $fibarray[$i-1] + $fibarray[$i-2];
}

This will create an array with the following values.


Array
(
 [0] => 0
 [1] => 1
 [2] => 1
 [3] => 2
 [4] => 3
 [5] => 5
 [6] => 8
 [7] => 13
 [8] => 21
 [9] => 34
 [10] => 55
)


Following on from this we can get a Fibonacci sequence to any position we want by using the following function.

function fibonacciSequence($pos){
 $fibarray = array(0,1);
 for($i=0;$i<=$pos;++$i){
  $fibarray[$i] = $fibarray[$i-1] + $fibarray[$i-2];
 }
 return $fibarray;
}

We can also create a very similar function that will only return a number at a particular position.

function fibonacciSequence($pos){
 $fibarray = array(0,1);
 for($i=0;$i<=$pos;++$i){
  $fibarray[$i] = $fibarray[$i-1] + $fibarray[$i-2];
 }
 return $fibarray[$pos];
}

For example, if we pass this function the number 56, the result would be 225,851,433,717.

An additional time (and space) saver for this function is that it detects any pixels that are just off white and simply displays a   character instead.

$img = ImageCreateFromJpeg('logo.jpg');
 
// get height and with of the image.
$width = imagesx($img);
$height = imagesy($img);
 
echo '<pre style="font-size:1px;">';
for($h=0;$h<$height;$h++){
 for($w=0;$w<=$width;$w++){
  if($w == $width){
   echo '<br>';
   continue;
  }
  // get image at pixel location
  $rgb = ImageColorAt($img, $w, $h);
  // convert colour into usable format
  $r = ($rgb >> 16) & 0xFF;
  $g = ($rgb >> 8 ) & 0xFF;
  $b = $rgb & 0xFF;
  // check for white/off-white colour
  if($r > 200 && $g > 200 && $b > 200){
   echo '&nbsp';
  }else{
   echo '<span  style="color:rgb('.$r.','.$g.','.$b.');">#</span>';
  }
 }
}
echo '</pre>';

As an example, take the following, quite recognisable, image.

This is transformed into the text on the following page.

The Google logo in ASCII format

Beware that although this works will for small image sizes if you try to convert a very large image you will find that the script takes a long time. This is because it looks at every pixel in turn and converts the colour into something usable, so if there are a lot of pixels it takes a long time to look at every one. Not only this, but you will also find that the size of the page generated will grow significantly due to all of the span elements being created.

The good thing about this site is that it saves having to go through all of the blogs in turn to see what is interesting in the world of PHP. If you run a PHP blog you can submit your site to the list and get your articles included in the updates.

function myFunction($intNum1,$intNum2){
 // function does something
}

Normal practice is to check the parameters to make sure that they are what you expected them to be before continuing on with the rest of the function. Lets say that we only want the numbers to be in a range. If they are not in the range the function should return false. Many programmers might start of writing something like this.

function myFunction($intNum1,$intNum2){
 if($intNum1 > 0 && $intNum1 < 1000){
  if($intNum2 > 0 && $intNum2 < 1000){
   // do something with the numbers.
   return $value;
  }else{
   return false;
  }
 }else{
  return false;
 }
}

This code will still produce the desired effect of checking to see that the numbers are within a range, but there is a simpler and more elegant way of doing this. For example, what if you wanted to add a third parameter, or a fourth? Having nested if statements is hard enough, but when you get to four levels things get a bit silly.

Here is the same code, but refactored in a way that allows for better readability and maintenance. Notice that the if statement logic has been reversed.

function myFunction($intNum1,$intNum2){
 // check parameter 1
 if($intNum1 < 0 && $intNum1 > 1000){
  return false;
 }
 // check parameter 2
 if($intNum2 < 0 && $intNum2 > 1000){
  return false;
 }
 // do something with the numbers.
 return $value;
}

This way, we get past all of the logic checking before getting down to what we want the function to do, and it is readable. Also, if you wanted to add another parameter you would just add another if statement to check that parameter. There if no juggling of nested statements or complicated syntax.

The above function also doesn’t take into account the fact that the parameters might not be numbers, additional checking can be added at the top of the function to account for this.

I have posted this in the general category because I have used this technique in at least 3 different languages since I started doing it in PHP. All of the code written here is in generic PHP like syntax, but the idea stands. Hopefully, you should get something out of this as well.

By using the e of the preg_replace function it is possible to run PHP functions within the output. In this case we count the number of characters found in the replace and use this to create a string of stars (*) of equal length.

function filterwords($text){
 $filterWords = array('gosh','darn','poo');
 $filterCount = sizeof($filterWords);
 for($i=0; $i<$filterCount; $i++){
  $text = preg_replace('/\b'.$filterWords[$i].'\b/ie',"str_repeat('*',strlen('$0'))",$text);
 }
 return $text;
}

When the following text is run through this function.

echo filterwords('Darn, I have a mild form of torretts, poo!');

It produces the following result.

****, I have a mild form of torretts, ***!

function spiderDetect() {
 $agentArray = array("ArchitextSpider", "Googlebot", "TeomaAgent",
  "Zyborg", "Gulliver", "Architext spider", "FAST-WebCrawler",
  "Slurp", "Ask Jeeves", "ia_archiver", "Scooter", "Mercator",
  "crawler@fast", "Crawler", "InfoSeek Sidewinder",
  "almaden.ibm.com", "appie 1.1", "augurfind", "baiduspider",
  "bannana_bot", "bdcindexer", "docomo", "frooglebot", "geobot",
  "henrythemiragorobot", "sidewinder", "lachesis", "moget/1.0",
  "nationaldirectory-webspider", "naverrobot", "ncsa beta",
  "netresearchserver", "ng/1.0", "osis-project", "polybot",
  "pompos", "seventwentyfour", "steeler/1.3", "szukacz",
  "teoma", "turnitinbot", "vagabondo", "zao/0", "zyborg/1.0",
  "Lycos_Spider_(T-Rex)", "Lycos_Spider_Beta2(T-Rex)",
  "Fluffy the Spider", "Ultraseek", "MantraAgent","Moget",
  "T-H-U-N-D-E-R-S-T-O-N-E", "MuscatFerret", "VoilaBot",
  "Sleek Spider", "KIT_Fireball", "WISEnut", "WebCrawler",
  "asterias2.0", "suchtop-bot", "YahooSeeker", "ai_archiver",
  "Jetbot"
 );
 
 $theAgent = $_SERVER["HTTP_USER_AGENT"];
 
 for($i=0;$i<count($agentArray);$i++){
  if(strpos(" ".strtolower($theAgent), strtolower($agentArray[$f]))!= false){
   return true;
  };
 };
 return false;
}

The function works by finding the current user agent string of the visitor and the comparing it to the list of user agents in an array. If the user agent is found then true is returned, otherwise the return value is false.

With this function present you can now include an if statement to see if the user agent is a search engine spider or not.

if(spiderDetect()){
 // do something for spiders
}else{
 // do something for users
}

Please be careful with this function. If you server different content to users and search engine spiders you will more than likely get banned for your efforts.

Also, this might be an incomplete list of search engine spider user agents, if you know any more then please write a comment and I will add them onto this list.

The constructor of the DirectoryIterator() object takes a single parameter, this is the path of the directory that is to be iterated over.

$dir = new DirectoryIterator('/');

To get the current working directory you can use the PHP function getcwd(). This will return the directory that the PHP script is being run from.

$dir = new DirectoryIterator(getcwd());

The previous bit of code will open up the root directory of your server. If you are on a Linux server you will see directories like dev, var, srv, etc, lib, home, root, sbin and usr.

With the object now created there are some different functions that can be used to look at different things. Here is a small list of what can be used:

• isDot(): This function is used to see if the file is a "." or a "..".
• isReadable (): Checks if the file is readable. If it is then it returns true, otherwise it is false.
• next(): Moves the iterator onto the next item in the list.
• valid(): This function checks to see if there is anything in the directory that can be iterated over. Basically, this function returns false if the iterator is at the end of the directory.
• current(): Returns the name of the current file.

These functions can be put together in the following way. This snippet of code will print out all of the files in a directory.

while($dir->valid()){
 if(!$dir->isDot()){
  print $dir->current()."<br />";
 }
 $dir->next();
}