Category: PHP

One of the main, probably the best, dynamic programming languages for web sites.

Web page inputs and insert into database

Also from the other posts, Join files together and simple calculator , I was also asked to do

“Accept form input for a user registration form, and store results in a MySQL table, using PHP. Applicant should demonstrate a knowledge of input validation, and using server-side code to avoid sql injection exploits. The user data should include first name, last name, email, an phone number.

Usage of Javascript pre-validation would be a plus, as would forward planning, i.e. adding a unique code to the user details that could be used to validate their email address. Suitable MySQL table schema should be demonstrated.”

To start with, I started at the data insert within a web page

<body>
<form name="input" action="insertData.php" method="post" onSubmit="return checkInputs()">
First Name :
<input type="text" name="firstname"/>
Second Name : 
<input type="text" name="secondname"/>
Email : 
<input type="text" name="email"/>
Phone number : 
<input type="text" name="phonenumber"/>
<input type="submit" value="Submit"/>
</form>
</body>

Which takes in the required input’s and also within the form HTML tag, but before sending to the back end PHP part of the exercise, there was a requirement to do some Javascript checking on the inputs.

So here is the javascript that will check the inputs, within the form onsubmit action I call this function checkInputs and the return value (true/false) is returned which gives the form either a action to post back to the server (true return) or to wait for the user correct there inputs (false return).

    var firstname = document.getElementsByName("firstname").item(0);

I get the data from the webpage, getElementsByName (which since it is a name there could be x amount of elements with that name, so I want the first one (.item(0))

  function checkInputs()
  {
    // obtain inputs
    var firstname = document.getElementsByName("firstname").item(0);
    var secondname = document.getElementsByName("secondname").item(0);
    var email= document.getElementsByName("email").item(0);
    var phonenum = document.getElementsByName("phonenumber").item(0);
    /* check the inputs */
    if (lengthCheck(firstname, "first name")) 
      if (lengthCheck(secondname, "second name"))
	if (emailChecker(email))
	  if (checkPhone(phonenum))
	    return true;
    return false;
  }

and then after getting the elements, I then call different additional functions that I did write within javascript to check the inputs gained. Here I check the length of a element passed within the one of the parameters within the function parameter list, with using objects you can access the objects value.length (javascript object of a element) and also use the focus function with the element which will focus the element on the webpage for the user to know where to check there input (also with a alert window to say why, e.g. “please insert some data”.)

  function lengthCheck(elem, thename)
  {
    if (elem.value.length> 0) 
      return true;
    else
    {
      alert("Please insert the " + thename);
      elem.focus();
    }
  }

Here is a way of using regular expression to check email inputs, basically it first checks to make sure there is a name before the “@” and also a at between 2 and 4 names with a “.” better them.

  /* check a email address, using regular expression */
  function emailChecker(elem)
  {
    var reg = /^[\w\-\.\+]+\@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/;
    if (elem.value.match(reg))
      return true;
    else
    {
      alert ("Please insert a valid email address");
      elem.focus();
      return false;
    }
  }

Here is a similar way as above for checking a phone number input between 11-15 numbers

  /* check against a phone number. a number being between 11-15 numbers*/
  function checkPhone(elem)
  {
    var reg = /^[0-9]{11,15}$/;
    if (elem.value.match(reg))
      return true;
    else
    {
      alert ("Please insert a valid phone number");
      elem.focus();
      return false;
    }
  }

This is the web page part, and here is the second part where I insert the data into database with php.

But here is the full web page part of the first part.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<script language="javascript">
  /* check the length of the element, focus is none present */
  function lengthCheck(elem, thename)
  {
    if (elem.value.length> 0) 
      return true;
    else
    {
      alert("Please insert the " + thename);
      elem.focus();
    }
  }
 
  /* check a email address, using regular expression */
  function emailChecker(elem)
  {
    var reg = /^[\w\-\.\+]+\@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/;
    if (elem.value.match(reg))
      return true;
    else
    {
      alert ("Please insert a valid email address");
      elem.focus();
      return false;
    }
  }
 
  /* check against a phone number. a number being between 11-15 numbers*/
  function checkPhone(elem)
  {
    var reg = /^[0-9]{11,15}$/;
    if (elem.value.match(reg))
      return true;
    else
    {
      alert ("Please insert a valid phone number");
      elem.focus();
      return false;
    }
  }
 
  function checkInputs()
  {
    // obtain inputs
    var firstname = document.getElementsByName("firstname").item(0);
    var secondname = document.getElementsByName("secondname").item(0);
    var email= document.getElementsByName("email").item(0);
    var phonenum = document.getElementsByName("phonenumber").item(0);
    /* check the inputs */
    if (lengthCheck(firstname, "first name")) 
      if (lengthCheck(secondname, "second name"))
	if (emailChecker(email))
	  if (checkPhone(phonenum))
	    return true;
    return false;
  }
</script>
</head>
<body>
<form name="input" action="insertData.php" method="post" onSubmit="return checkInputs()">
First Name :
<input type="text" name="firstname"/>
 
Second Name : 
<input type="text" name="secondname"/>
 
Email : 
<input type="text" name="email"/>
 
Phone number : 
<input type="text" name="phonenumber"/>
 
<input type="submit" value="Submit"/>
</form>
</body>
</html>

Join files together into a single file and expand out

Again as with the previous post (simple calculator) this was another question to answer, which was fun to do.

“Write a class containing 2 functions. One function to merge 2 or more images into a single binary file. Write a counterpart function to this,which can extract the original files from the single binary, and write them out as single images, using their original filenames. Compression is not necessary, as the exercise is only designed to show an
understanding of using binary files with PHP, filesystem error handling, and planning a simple file format.”

Since we needed to have a simply file structure, so I decided to have a file structure of

Filename: <filename>
Size: <size in bytes>
<data>

where the filename, size in bytes and data (of the file itself) is filled in when the program runs.

So to start with I created a directory structure to pick up files from within one directory and place into another

/images
/newimages

and placed some images into the images directory.

To scan within a directory there is a iterator within PHP called DirectoryIterator which will do what it says on the tin, it will give you files within a directory and since being a iterator you can use a foreach to go through each file. Here is the syntax for DirectoryIterator to loop with a foreach (the $fileDirectory is the directory to scan and the $fileDetails is the files that are within the directory.

foreach (new DirectoryIterator($fileDirectory) as $fileDetails)

So what happens is that the program will loop through each file in the directory and open the single to write to, whilst looping through directory output the Filename to the single file and the Filesize, then read the actual file into a object to write to the single file within a binary format, and loop until no more files in that directory.

Then to un-single the file, I read the single file and find out the filename and filesize, open a file to write to in the new directory and read from the single file bits with the size of the filesize information from the single file, this was the actual file data, place this file data into the new file within the new directory. (kinder how tar works, builds all files into a single file from a directory and then expand then afterwards).

Here is the full code, it is small enough to hopefully follow.

<?php
  class imageBuilder 
  {
    /* read files into one file */
    /* file format 
      Filename: <filename>
      Size: <size in bytes>
      <data>
    */
    function readFiles($fileDirectory,$outputName)
    {
      $fHandle = fopen($outputName, "wb");
      if ($fHandle == false) throw new Exception("Error open file to write to");
      foreach (new DirectoryIterator($fileDirectory) as $fileDetails)
      {
	$filesize = filesize($fileDirectory."/".$fileDetails);
	if ($filesize > 0 && $fileDetails !="..")
	{
	  $rHandle = fopen($fileDirectory."/".$fileDetails, "rb");
	  if ($rHandle == false) throw new Exception("Error open file to read from");
	  $readInFile = fread($rHandle,$filesize);
	  if ($readInFile==false) throw new Exception("Error on reading file to read from");
	  fclose($rHandle);
	  if (fwrite($fHandle, "Filename: $fileDetails\n")==false) throw new Exception("Error writting data");
	  if (fwrite($fHandle, "Size : $filesize\n")==false) throw new Exception("Error writting data");
	  if (fwrite($fHandle,$readInFile)==false) throw new Exception("Error writting data");
	}
      }
      fclose($fHandle);
    }
 
    /* write files back out from the single file*/
    function writeFiles($fileDriectoryToWrite, $fileToReadFrom)
    {
      $rHandle = fopen($fileToReadFrom,"rb");
      if ($rHandle==false) throw new Exception("Error opening file to read");
      while (!feof($rHandle))
      {
	$filename = fgets($rHandle);
	$filename = trim(substr($filename, stripos($filename, ":")+1));
	if (strlen($filename) == 0) break;
	if ($filename == false) throw new Exception("Error reading the filename from file");
	$filesize = fgets($rHandle);
	if ($filesize ==false) throw new Exception("Error reading the filesize from the file");
	$filesize = trim(substr($filesize, stripos($filesize,":")+1));
	$readFileInfo = fread($rHandle, $filesize);
	if ($readFileInfo == false) throw new Exception("Error reading data from file to read from");
	$fHandle = fopen($fileDriectoryToWrite."/".$filename,"wb");
	if ($fHandle == false) throw new Exception("Error opening writing to file");
	if (fwrite($fHandle, $readFileInfo) == false) throw new Exception("Error writing to file");
	fclose($fHandle);
      }
      fclose($rHandle);
    }
  }
 
  $imageB = new imageBuilder();
  try {
    $imageB->readFiles("images","filetogether");
  }
  catch (Exception $ex)
  {
    echo "Error building the one file : $ex";
  }
 
  try {
    $imageB->writeFiles("newimages","filetogether");
  }
  catch (Exception $ex)
  {
    echo "Error writing files back out : $ex";
  }
 
?>

and you need to do is place some files within the /images directory and then run the program and it will create a single file called “filetogether” and also expand that file into the /newimages directory.

Simple calculator

Within a interview they requested me to do some exercises at home and here is the question that they posed.

“Create a simple stack-based calculator. This should be capable of performing addition, subtraction, multiplication and division. Example input would be: “2*(3+1)”. The result should be expressed as a numeric value, so the example should return 8. Usage of the eval() function, although amusing, is not allowed! This test is designed to show general programming skills, rather than an understanding of the programming platform; however the solution should be demonstrated using php as the language.”

So I decided to post on this site as well the design and program that I did come up with.

Since in maths you have to equate the ( .. ) first and then * , / , + , – so to start with I created a function that will pull out the brackets from the string input

    /* need to find the brackets and then equate the value and build outwards */
    public function equate()
    {
       // this is the string that was inputted when the class was created ( $this->calcstr;)
	$theStr = $this->calcstr;
 
	$bracketI = strrpos($theStr, "(");
	// there is a bracket
	while ($bracketI >=0)
	{
	  // find a bracket to match
	  $bracketEnd = strpos($theStr, ")", $bracketI);
	  if ($bracketEnd > 0)
	  {
	    // match then get the internal bracket value
	    $EqualMiddle = substr($theStr, $bracketI+1, ($bracketEnd-$bracketI)-1);
	    $calMiddle = $this->calculateTheString($EqualMiddle);
	    // rebuild the string without the bracket but with the value
	    $theStr = substr($theStr,0, $bracketI) . $calMiddle. substr($theStr, $bracketEnd+1);
	  }
	  else
	    throw new Exception("Bracket miss matched");
 
	  $bracketI = strrpos($theStr, "(");
	  if ($bracketI == false && $theStr[0] != "(") break;
	}
	return $this->calculateTheString($theStr);
    }

So what happens is that it will find the last occurrence of a bracket “(” and then find the corresponding “)” for that bracket, error is not found. Once found, it will then send to a function called “calculateTheString” that will actually calculate the value.

The calculateTheString function

 private function calculateTheString($theStr)
    {
	// look for * / + - in that order and then get the number each side to do the math
	$mathStr = array("*", "/", "+", "-");
	foreach ($mathStr as $maths)
	{
	  do 
	  {
	    // find each occurence of the math func
	    $mathI = strpos($theStr, $maths);
	    if ($mathI > 0)
	    {
	      // find the numeric values before and after the math func
	      try {
		$valueBefore = $this->getNumbericValue(substr($theStr, 0,$mathI), 0);
		$valueAfter =  $this->getNumbericValue(substr($theStr, $mathI+1), 1);
	      } catch (Exception $ex)
	      {
		echo "Error : $ex (String = $theStr)";
	      }
	      // do the math func
	      switch($maths)
	      {
		case "*" : $newV = $valueBefore * $valueAfter; break;
		case "/" : $newV = $valueBefore / $valueAfter; break;
		case "+" : $newV =$valueBefore + $valueAfter; break;
		case "-" : $newV =$valueBefore - $valueAfter;; break;
		default : $newV =0;
	      }
	      // rebuild string without the math func that is done
	      $theStr = substr($theStr,0,($mathI-strlen($valueBefore))) . ($newV) . substr($theStr,($mathI+strlen($valueAfter)+1));
	    }
	  } while ($mathI >0);
	}
	return $theStr;
    }

will loop through the math functions (*,/,+,-) in order of calculation, if it finds one of them it will equate what the value of that block of math is e.g.

4*2+1

it would equate the 4*2 and then rebuild the string to have the result within the next loop e.g.

8+1

so that when it gets to the + math function it will add 8 to 1.

To get the number values before and after the math functions (*,/,+,-) I created a function to pull out the values called “getNumbericValue”.. since the values will either be before or after the e.g. going backwards or forwards in the string, then you will need to either go in that direction. Once you have got the area within the string of the numeric values, then use the intval to convert into a integer value. The is_numeric makes sure that there is still a numeric value present.

/* $theStr = string to search, leftOrRight means going left or right in the string, 0 = left, 1=right*/
    private function getNumbericValue($theStr, $leftOrRight=1)
    {
	if (strlen($theStr) == 0) throw new Exception("No number value");
	if ($leftOrRight ==1) { $pos =0; 
	  $start = 0;
	}else 
	{
	  $pos = strlen($theStr)-1;
	  $start = strlen($theStr) -1;
	}
 	while (true)
	{
	  if (is_numeric($theStr[$pos]))
	  {
	    if ($leftOrRight == 0) $pos--; else $pos++;
	  }
	    else break;
	}
	// if just the number at the start
	if ($pos == -1) return intval($theStr);
	// if the start is greater than the end point, change over
	if ($start > $pos) { $tmp = $pos; $pos = $start; $start = $tmp;}
	return intval(substr($theStr,$start, $pos));
    }

To build all that together with

<?php
  class calc 
  {
    private $calcstr = "";
 
    function __construct($strIn)
    {
      $this->calcstr = $strIn;
    }
 
    public function setStr($strIn = "")
    {
      $this->calcstr = $strIn;
    }
 
    /* $theStr = string to search, leftOrRight means going left or right in the string, 0 = left, 1=right*/
    private function getNumbericValue($theStr, $leftOrRight=1)
    {
	if (strlen($theStr) == 0) throw new Exception("No number value");
	if ($leftOrRight ==1) { $pos =0; 
	  $start = 0;
	}else 
	{
	  $pos = strlen($theStr)-1;
	  $start = strlen($theStr) -1;
	}
 	while (true)
	{
	  if (is_numeric($theStr[$pos]))
	  {
	    if ($leftOrRight == 0) $pos--; else $pos++;
	  }
	    else break;
	}
	// if just the number at the start
	if ($pos == -1) return intval($theStr);
	// if the start is greater than the end point, change over
	if ($start > $pos) { $tmp = $pos; $pos = $start; $start = $tmp;}
	return intval(substr($theStr,$start, $pos));
    }
 
    private function calculateTheString($theStr)
    {
	// look for * / + - in that order and then get the number each side to do the math
	$mathStr = array("*", "/", "+", "-");
	foreach ($mathStr as $maths)
	{
	  do 
	  {
	    // find each occurence of the math func
	    $mathI = strpos($theStr, $maths);
	    if ($mathI > 0)
	    {
	      // find the numeric values before and after the math func
	      try {
		$valueBefore = $this->getNumbericValue(substr($theStr, 0,$mathI), 0);
		$valueAfter =  $this->getNumbericValue(substr($theStr, $mathI+1), 1);
	      } catch (Exception $ex)
	      {
		echo "Error : $ex (String = $theStr)";
	      }
	      // do the math func
	      switch($maths)
	      {
		case "*" : $newV = $valueBefore * $valueAfter; break;
		case "/" : $newV = $valueBefore / $valueAfter; break;
		case "+" : $newV =$valueBefore + $valueAfter; break;
		case "-" : $newV =$valueBefore - $valueAfter;; break;
		default : $newV =0;
	      }
	      // rebuild string without the math func that is done
	      $theStr = substr($theStr,0,($mathI-strlen($valueBefore))) . ($newV) . substr($theStr,($mathI+strlen($valueAfter)+1));
	    }
	  } while ($mathI >0);
	}
	return $theStr;
    }
 
    /* need to find the brackets and then equate the value and build outwards */
    public function equate()
    {
	$theStr = $this->calcstr;
 
	$bracketI = strrpos($theStr, "(");
	// there is a bracket
	while ($bracketI >=0)
	{
	  // find a bracket to match
	  $bracketEnd = strpos($theStr, ")", $bracketI);
	  if ($bracketEnd > 0)
	  {
	    // match then get the internal bracket value
	    $EqualMiddle = substr($theStr, $bracketI+1, ($bracketEnd-$bracketI)-1);
	    $calMiddle = $this->calculateTheString($EqualMiddle);
	    // rebuild the string without the bracket but with the value
	    $theStr = substr($theStr,0, $bracketI) . $calMiddle. substr($theStr, $bracketEnd+1);
	  }
	  else
	    throw new Exception("Bracket miss matched");
 
	  $bracketI = strrpos($theStr, "(");
	  if ($bracketI == false && $theStr[0] != "(") break;
	}
	return $this->calculateTheString($theStr);
    }
 
  }
 
  $theequal = "2*(3+1)";
  $thecalc = new calc($theequal);
  try {
    echo $thecalc->equate();
  } catch (Exception $err)
  {	
    echo $err;
  }
?>

and the output would be

8

I found it a interesting exercise 🙂

AJAX – setup and test

AJAX is the way of communicating with a back end server without having to send the full information (you can of course) but for example you could just send a username check to see if it is available, but the main thing is that you do not send back a full page but only the part that you want to update.

With reference to the example of a username, you could just send the username and send back either yes or no response which saves allot of time and traffic from the client to the server (and makes the whole web page experience nicer).

All the AJAX is shorthand for “Asynchronous JAvascript and Xml”, asynchronous means that you can do something else whilst waiting for the response (put the kettle on and get a cup for the drink whilst the kettle is boiling) thus with javascript on the client web browser sends a request to a web page on the server with XML wrappings.

To get the basics lets start with the being

  // this function will return a XmlHttpRequest object that allows you to "talk" to the server.
  function GetXmlHttpObject()
  {
      // IE7+, FF, Chrome, Opera, Safari
      if (window.XMLHttpRequest) return new XMLHttpRequest;
 
      // IE6 , IE5
      if (window.ActiveXObject) return new ActiveXObject("Microsoft.XMLHTTP");
  }

the GetXmlHttpObject will return a object that will allow the javascript to talk to the backend server, the newer version is call a XMLHttpRequest whilst on older browsers it was part of the ActiveXObjects.

The next is to send a request to the backend server

    xmlHttpObject.onreadystatechange=callBackFunction;
    xmlHttpObject.open("GET", GetUrl, true);
    xmlHttpObject.send(null);

The onreadystatechange, will call a function (in javascript on the client browser) when the request alters from different states, the different states are

  • 1.open method invoked successful, open a connection with the server
  • 2.server responsed with a valid header response.
  • 3.server has sent some data, the response content is started to load.
  • 4.server has finished sending all of data

so from reading the states, you are really interested in state 4, because that will have the data (server response) that you are interested in for this.

The .open forms the request to the XmlHttpRequest object to call (“GET” in HTML) the server web site, the GetUrl is just a variable that well call a php page (“ajaxbackendcall.php”) which takes a parameter called name and returns a string with the name in reverse (shall include that source code later).

And then the .send will start the ready states to change and sends the request to the backend server, here is the function that is called on the state change

  function callBackFunction()
  {
    if (xmlHttpObject.readyState == 4)
      alert(xmlHttpObject.responseText);
  }

What is happening here, is that from the state stages I am waiting on ready state to equal 4 ( when the server has finished responding) and then output the response from the responseText which is filled from the AJAX call to the backend server.

That is mainly it, here is some full code for you to try out save this as “codingfriends.com.ajax.test.html”

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html3/strict.dtd">
<html>
<head>
<script type="text/javascript">
  // the xmlHttpRequest object
  var xmlHttpObject;
 
  // the ajax call 
  function getInnerText()
  {
    // get the name to send to the server backend page
    var namehere = document.getElementById("namehere");
 
    // request the xmlHttpObject 
    xmlHttpObject = GetXmlHttpObject();
 
    // if there is not xmlHttpRequest object being allowed to be created then the browser does not support it.
    if (xmlHttpObject==null)
    {
      alert("Browser does not support XmlHttp calls e.g. AJAX");
      return;
    }
 
    // fill in the request details, e.g. the url to call and also the query string inserted into the url
    var GetUrl = "ajaxbackendcall.php"+"?name="+namehere.value;
 
    // here is the call to the server.
    // to start with setup which function to call when a ready state on the XmlHttpRequest object has changed
    xmlHttpObject.onreadystatechange=callBackFunction;
    // request the html "GET" to obtain the url (e.g. the backend server page, dynmaic normally)
    xmlHttpObject.open("GET", GetUrl, true);
    // and then issue it
    xmlHttpObject.send(null);
  }
 
  // the function that is called once the XmlHttpRequest object state has changed
  /* the readyStates are 
    1 open method invoked successful, open a connection with the server
    2 server responsed with a valid header response.
    3 server has sent some data, the response content is started to load.
    4 server has finished sending all of data
  */
  // so we listen for readyState 4 when all finished
  // and output the response text into the div id innertextoutput
  function callBackFunction()
  {
    if (xmlHttpObject.readyState == 4)
      document.getElementById("innertextoutput").innerHTML=xmlHttpObject.responseText;
  }
 
  // this function will return a XmlHttpRequest object that allows you to "talk" to the server.
  function GetXmlHttpObject()
  {
      // IE7+, FF, Chrome, Opera, Safari
      if (window.XMLHttpRequest) return new XMLHttpRequest;
 
      // IE6 , IE5
      if (window.ActiveXObject) return new ActiveXObject("Microsoft.XMLHTTP");
  }
</script>
</head>
<body>
<a href="#" onclick="javascript:getInnerText()">click here to return text from a ajax call</a>
<br/>
Enter the name here <input id="namehere"/>
<br/>
<div id="innertextoutput"></div>
</body>
</html>

and then save this as the ajaxbackendcall.php file to call (in the same directory as the code above and also within a directory that has PHP plugin enable for that webserver be it apache or IIS.

<?php
    $name = $_GET['name'];
 
    // change the output to say something else, here I am just reversing the name
    if (strlen($name) > 0)
    {
      // have to insert something into it so that php does not make it into a array but a string
      $namereturn="0";
      $j = 0;
      for ($i = strlen($name)-1; $i >= 0; $i--)
      {
        $namereturn[$j++]=$name[$i];
      }
      echo "normal name {$name} and in reverse {$namereturn}";
    }
    else
      return "No name inputted";
?>

The output would be similar to the below. OUTPUT

click here to return text from a ajax call
Enter the name here

END OF OUTPUT

If you do not have a PHP webserver to test with, you can just alter the codingfriends.com.ajax.test.html code by altering the backend web page to call to this

var GetUrl = "nonephpbackend.html"

and create a page within the same directory as the codingfriends.com.ajax.test.html page and place something inside it like

hi there

WordPress – plugin – hello world

WordPress is a blogging software that runs on a webserver, the great thing about wordpress is that you are able to extend the functions to create the pages/comments/archives etc on the blogging site. You are also able to create your own themes that will use the functions that you can create within that theme So lets it straight, a plugin for the wordpress is the way that you can extend the functional aspects of the whole site that is not dependent on the theme that you using (a theme is what you view on the web page the “style” (css) of the site for example).

There is two main directories within the wordpress directory structure to add in new themes (wp-content/themes) and the plugins (wp-content/plugins) this is where you place the code to extend the basic wordpress install.

In this example I going to extend the action get_header, if you save the code below into the directory wp-content/plugins/codingfriends_helloworld as codingfriends_helloworld.php

<?php
/*
Plugin Name: Coding friends hello world
Plugin URI: http://www.codingfriends.com/
Description: Outputs hello world
Version: 0.1
Author: Genux
Author URI: http://www.codingfriends.com
License: GPL2
*/
 
function codingfriends_helloworld()
{
  echo "hello world";
}
 
add_action('get_header', 'codingfriends_helloworld');
?>

once you have saved that file, then goto your wordpress admin page, on the left is the Plugins link, click on that and within there will be the “new” plugin called coding friends hello world, you just need to activate it and then hey presto it works. There will be “hello world” at the top of the wordpress installed pages within the main site (not the wp-admin part of the site).

What is happening is that you have created a function called codingfriends_hellworld, which outputs “hello world”, but the main part is the

add_action

this will add this function to a defined plugin action (to get a list of all of the actions (these happen within the core site), and filters (alter text within the site, e.g. pages that you add to the site, comments etc) you can use look here).

So when the action get_header is called within the main wordpress application, it will call your new function (codingfriends_helloworld).

There is tons of things that you can do with these, alter the comments when posted back to the site, pages etc, just look at the API list.

Blob to store data in mysql database

To store data within a blob in a database can be a good thing at times because then you can just copy the database from one place to another and use the access rights on the database to restrict access to the “files” within the database.

There could be a few reasons why you want to store the data within a blob in the database, but here how the basics would work.

To start with you have to create a database and a table to store the data/file within the blob, of course if you have already created the database and/or the tables then alter as you think, but here is the basics.

  CREATE DATABASE phptestplace;
  CREATE TABLE storingData (id INT NOT NULL auto_incremenet, lblob BLOB, PRIMARY KEY (id));

And then within a php file you can access the database and a file.

  $link = mysql_connect('localhost', 'username', 'userpassword');
  if (!$link) {
      die('Could not connect: ' . mysql_error());
  }
// alter to your database name
  mysql_select_db("phptestplace", $link);

and now access the file and read in file

  $filename = "filetoload.txt";
  $handle = fopen($filename, "r");
  $contents = fread($handle, filesize($filename));
  fclose($handle);
 
// to insert into the database you need to add in the slashes for characters like / \ etc.
  $contents = addslashes($contents);

to insert into the blob you just, change the table and table name to what may have called it.

  $sqlquery = "insert into storingData(largeblob) values ('$contents')";
  mysql_query($sqlquery) or die("ERROR");*/

to get the data back (I am calling back the last inserted value into the table)

// get the data into a result variable
  $return = mysql_query ("select lblob from storingData where id = (select max(id) from storingData)") or die("LLL");
// get the contents of the blob from the return variable (it returns a array of data) and the list takes out the data from a array each part at time.
  list($newcontents) = mysql_fetch_array($return);

and then store the data from the database pull into a file, I have called it newfile.txt, but it is up to you.

  $fp = fopen('NEWFILE.txt', 'w');
  fwrite($fp, $newcontents);
  fclose($fp);

Of course can do it via a web page, using a HTML FORM enctype=”multipart/form-data” within the form tag otherwise it may not work.

Polymorphism

Polymorphism means that you are deriving from a base class to create a new class, and the polymorphism is when you derive from the base class and implement a interface functions, so that any derived class will have to these functions implement so if you call a function that is defined by the interface to be present, you know it will be implement in some forum.

In php, there is a interface type, so we can define a basic Animal type to print is name, so that any animal that is derived from this interface will have to implement at least the print name function, here is the interface

interface Animal
{
  public function printName();
}

it is very similar to a class structure apart from there is no functional code, just the function definition. To then implement the interface Animal within a class, so that you will know that the printName() function will be implemented you use the “implements” keyword in the class definition as below.

class Cat implements Animal
{....

and then the class Cat will have to define the printName function as

  public function printName()
  {
     echo "Cat class\n";
  }

otherwise if you did not implement it there would be a error on the “compile time” as below.

Fatal error: Class Cat contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (Animal::printName)

here is a full code that will do a Cat and Dog class, then you can create a array of different derived Animals interfaces and then just call the printName and you know it will be present.

<?php
interface Animal
{
  public function printName();
}
 
class Cat implements Animal
{
      public function printName()
      {
	echo "Cat class\n";
      }
};
 
class Dog implements Animal 
{
      public function printName()
      {
	echo "Dog class\n";
      }
};
 
$animals = Array(
    new Cat(), new Dog()
    );
 
foreach ($animals as $a)
{
    $a->printName();
}
 
?>

and the output would be

Cat class
Dog class

Polymorphism is great, because you just know that certain functions will be implemented.