PHP-Arrays-Get the occurance of each value in numeric array

Like as always we have a problem we have some prerequisites we will have a function and we will draw some results


Problem and Prerequisites :

We have an array let us suppose array(1,2,1,3,4,5,4,6,3,2,1,2,8,9,3,4,5,3,2,4,6,2) and we want to create a function that checks for number of times value repeats in the array.

So we need and output like

1 repeats 3 times
2 repeats 5 times etc.

Function and Solution :

 <?php
 function get_modes($numarray)  
 {  
   if(!(is_array($numarray)))  
     throw new Exception ('Parameter Not an array');  
   $revarray=array();  
   foreach($numarray as $key=>$value)  
   {  
     if(array_key_exists($value,$revarray))  
     {  
       $revarray[$value]++;  
     }  
     else   
     {  
       $revarray[$value]=1;  
     }  
   }  
   return $revarray;  
 }  
 $myarray=array(1,2,1,3,4,5,4,6,3,2,1,2,8,9,3,4,5,3,2,4,6,2);  
 $navarray=get_modes($myarray);  
 foreach($navarray as $key=>$value)  
 {  
   echo $key." repeats ".$value." times<br/>";  
 }  
 ?>  

Output:

1 repeats 3 times
2 repeats 5 times
3 repeats 4 times
4 repeats 4 times
5 repeats 2 times
6 repeats 2 times
8 repeats 1 times
9 repeats 1 times

PHP-Image functions

//size of image
getimagesize()
http://www.php.net/getimagesize

//image width
imagesx()
http://www.php.net/manual/en/function.imagesx.php


//image height
imagesy()
http://www.php.net/manual/en/function.imagesy.php

//determine type of an image
exif_imagetype()
http://www.php.net/manual/en/function.exif-imagetype.php

Encrypt data using PHP

Encryption	Decryption
AES_ENCRYPT()	AES_DECRYPT()
ENCODE()	DECODE()
DES_ENCRYPT()	DES_DECRYPT()
ENCRYPT()	N/A
ENCRYPT()	N/A
MD5()	N/A
OLD_PASSWORD()	N/A
PASSWORD()	N/A
SHA()	N/A
SHA1()	N/A
N/A	UNCOMPRESSED_LENGTH()

HTML->Difference between GET and POST methods

POST Method
In Post method we can send unlimited data(This limit is defined by server for example "post_max_size=20M" in Apache)

Data is not shown in URL so it is good for sensitive data

GET Method

In GET method this depends on browser for example IE8 can take about 2048 bytes of data i.e about 2KB

Data is shown in URL so not appropriate for sensitive data

PHP-Database connectivity function's

One of the main aspects of PHP is database connectivity.Though it supports variety of databases we will talk about mysql in particular here.

All the functions which are of concern are present in file mysqli.php which contains class "mysqli_sql_exception" which in turn extends "RuntimeException"

The very first functions that we encounter while working with databases with PHP are the "connect functions".

Let's see what we get when we execute these functions in order

As a software development flows we will have some prerequisites,a function which will process them and then we will have some results.

Prerequiaites :

A dbhost : "localhost"
A username : "uroot"
A password : "proot"
Also

That's it and all we need is a php setup LAMP/WAMP/MAMP/XAMPP package

Our first function :

 $con= mysqli_connect('localhost1','puroot','pproot','test1');  

Reference :

/**
 * (PHP 5)<br/>
 * Alias of <b>mysqli::__construct</b>
 * @link http://php.net/manual/en/function.mysqli-connect.php
 * @param $host [optional]
 * @param $user [optional]
 * @param $password [optional]
 * @param $database [optional]
 * @param $port [optional]
 * @param $socket [optional]
 */
function mysqli_connect ($host, $user, $password, $database, $port, $socket) {}

This function tries to connect to the database with given credentials. We have created a negative mutant to test the same as you can see from what credentials we have passed above.


Our Second function and third function :

 if (mysqli_connect_errno())  
 {  
   echo "Failed to connect to MySQL: " . mysqli_connect_error();  
 }

Reference:

/**
 * (PHP 5)<br/>
 * Returns the error code from last connect call
 * @link http://php.net/manual/en/mysqli.connect-errno.php
 * @return int An error code value for the last call to <b>mysqli_connect</b>, if it failed.
 * zero means no error occurred.
 */
function mysqli_connect_errno () {}

/**
 * (PHP 5)<br/>
 * Returns a string description of the last connect error
 * @link http://php.net/manual/en/mysqli.connect-error.php
 * @return string A string that describes the error. <b>NULL</b> is returned if no error occurred.
 */
function mysqli_connect_error () {}

Now when we execute the above pieces of code we get an error

Failed to connect to MySQL: Unknown MySQL server host 'localhost1' (2)Error creating database:

When we set host right we get following error
Failed to connect to MySQL: Access denied for user 'puroot'@'localhost' (using password: YES)Error creating database: 

Similarly when we set username and password right we get
Failed to connect to MySQL: Unknown database 'test1'

Now that we are done with the set of connection functions we will try to create a database on success.Now since we have already created a database "test" we will test with a negative mutant.

Our fourth and fifth function

 $sql="CREATE DATABASE test";  
 if (mysqli_query($con,$sql))  
 {  
   echo "Database test created successfully";  
 }  
 else  
 {  
   echo "Error creating database: " . mysqli_error($con);  
 }  

Reference:

 /**  
  * (PHP 5)<br/>  
  * Performs a query on the database  
  * @link http://php.net/manual/en/mysqli.query.php  
  * @param mysqli $link  
  * @param string $query <p>  
  * The query string.  
  * </p>  
  * <p>  
  * Data inside the query should be properly escaped.  
  * </p>  
  * @param int $resultmode [optional] <p>  
  * Either the constant <b>MYSQLI_USE_RESULT</b> or  
  * <b>MYSQLI_STORE_RESULT</b> depending on the desired  
  * behavior. By default, <b>MYSQLI_STORE_RESULT</b> is used.  
  * </p>  
  * <p>  
  * If you use <b>MYSQLI_USE_RESULT</b> all subsequent calls  
  * will return error Commands out of sync unless you  
  * call <b>mysqli_free_result</b>  
  * </p>  
  * <p>  
  * With <b>MYSQLI_ASYNC</b> (available with mysqlnd), it is  
  * possible to perform query asynchronously.  
  * <b>mysqli_poll</b> is then used to get results from such  
  * queries.  
  * </p>  
  * @return mixed <b>FALSE</b> on failure. For successful SELECT, SHOW, DESCRIBE or  
  * EXPLAIN queries <b>mysqli_query</b> will return  
  * a <b>mysqli_result</b> object. For other successful queries <b>mysqli_query</b> will  
  * return <b>TRUE</b>.  
  */  
 function mysqli_query (mysqli $link, $query, $resultmode = 'MYSQLI_STORE_RESULT') {}  
 /**  
  * (PHP 5)<br/>  
  * Returns a string description of the last error  
  * @link http://php.net/manual/en/mysqli.error.php  
  * @param mysqli $link  
  * @return string A string that describes the error. An empty string if no error occurred.  
  */  
 function mysqli_error (mysqli $link) {}  

Error creating database: Can't create database 'test'; database exists

because we have already created one

similarly mysql_query() is used for create table,insert

Our sixth function

 $result= mysqli_query($con,"SELECT * FROM Persons");  
 while($row= mysqli_fetch_array($result))  
 {  
   echo "<pre>";  
   print_r($row);  
   echo "</pre>";  
 }  
 $result= mysqli_query($con,"SELECT * FROM Persons");  
 while($row= mysqli_fetch_row($result))  
 {  
   echo "<pre>";  
   print_r($row);  
   echo "</pre>";  
 }  
 $result= mysqli_query($con,"SELECT * FROM Persons");  
 while($row= mysqli_fetch_object($result))  
 {  
   echo "<pre>";  
   print_r($row);  
   echo "</pre>";  
 }  
 $result= mysqli_query($con,"SELECT * FROM Persons");  
 while($row= mysqli_fetch_assoc($result))  
 {  
   echo "<pre>";  
   print_r($row);  
   echo "</pre>";  
 }  

References for ways we can fetch row:

 /**  
  * (PHP 5)<br/>  
  * Fetch a result row as an associative, a numeric array, or both  
  * @link http://php.net/manual/en/mysqli-result.fetch-array.php  
  * @param mysqli_result $result  
  * @param int $resulttype [optional] <p>  
  * This optional parameter is a constant indicating what type of array  
  * should be produced from the current row data. The possible values for  
  * this parameter are the constants <b>MYSQLI_ASSOC</b>,  
  * <b>MYSQLI_NUM</b>, or <b>MYSQLI_BOTH</b>.  
  * </p>  
  * <p>  
  * By using the <b>MYSQLI_ASSOC</b> constant this function  
  * will behave identically to the <b>mysqli_fetch_assoc</b>,  
  * while <b>MYSQLI_NUM</b> will behave identically to the  
  * <b>mysqli_fetch_row</b> function. The final option  
  * <b>MYSQLI_BOTH</b> will create a single array with the  
  * attributes of both.  
  * </p>  
  * @return mixed an array of strings that corresponds to the fetched row or <b>NULL</b> if there  
  * are no more rows in resultset.  
  */  
 function mysqli_fetch_array (mysqli_result $result, $resulttype = 'MYSQLI_BOTH') {}
/**
 * (PHP 5)<br/>
 * Get a result row as an enumerated array
 * @link http://php.net/manual/en/mysqli-result.fetch-row.php
 * @param mysqli_result $result
 * @return mixed <b>mysqli_fetch_row</b> returns an array of strings that corresponds to the fetched row
 * or <b>NULL</b> if there are no more rows in result set.
 */
function mysqli_fetch_row (mysqli_result $result) {}
/**
 * (PHP 5)<br/>
 * Fetch a result row as an associative array
 * @link http://php.net/manual/en/mysqli-result.fetch-assoc.php
 * @param mysqli_result $result
 * @return array an associative array of strings representing the fetched row in the result
 * set, where each key in the array represents the name of one of the result
 * set's columns or <b>NULL</b> if there are no more rows in resultset.
 * </p>
 * <p>
 * If two or more columns of the result have the same field names, the last
 * column will take precedence. To access the other column(s) of the same
 * name, you either need to access the result with numeric indices by using
 * <b>mysqli_fetch_row</b> or add alias names.
 */
function mysqli_fetch_assoc (mysqli_result $result) {}
/**
 * (PHP 5)<br/>
 * Returns the current row of a result set as an object
 * @link http://php.net/manual/en/mysqli-result.fetch-object.php
 * @param mysqli_result $result
 * @param string $class_name [optional] <p>
 * The name of the class to instantiate, set the properties of and return.
 * If not specified, a <b>stdClass</b> object is returned.
 * </p>
 * @param array $params [optional] <p>
 * An optional array of parameters to pass to the constructor
 * for <i>class_name</i> objects.
 * </p>
 * @return object an object with string properties that corresponds to the fetched
 * row or <b>NULL</b> if there are no more rows in resultset.
 */
function mysqli_fetch_object (mysqli_result $result, $class_name = null, array $params = null) {}

PHP-Reference Variable

Reference variable are those that have a reference to the value stored in them for example

 $name = 'fruit'; //Generic Varible  
 $$name='banana'; //Reference Variable  
 echo $fruit;   
 //Outputs Banana  

Here $name is a variable which stores name 'fruit' and in turn there is a memory location in your system when you run this program which is labelled as 'fruit' in which value is stored as $$name or $fruit.

Static function,Variable accesibility

Recently one of my co-friends regarding  a programme which made my concepts clear for a static function, variable accessibility outside a class

 <?php  
 final class Hello  
 {  
      private static $greeting='Hello';  
      private static $initialized=false;  
      private static function initialize()  
      {  
           if(self::$initialized)  
           return;  
         self::$greeting='There';  
         self::$initialized=true;  
      }  
     public static function greet()  
     {  
       self::initialize();  
       echo self::$greeting;  
     }  
     public function hello1()  
     {  
       return 'hi';  
     }  
 }  
 echo Hello::hello1();  
 $obj=new Hello();  
 echo "==>";  
 echo $obj->greet();  
 ?>  

this outputs "hi==>There"

A static function though can be called with scope resolution operator via class name directly or from object.

A static variable can only be called from a static function or from a class name via scope resolution operator

And since we can call a static function directly we cannot use $this in the same

for example in static function greet we are calling the

echo self::$greeting;

and not

echo $this->$greeting;