Create README.md

Author: OleksandrChernokolov

README.md

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+# Database search algorithm (PHP/SQL)
+Smart and fast search algorithm based on PHP. In this case, a database of world cities search using SQL queries is presented. There are some features of the algorithm:
++ Retrieve the 10 most relevant results or similar results if there are no exact matches.
++ The result will be found even if a small error is made in the request or the request is inaccurate.
++ The presence of an array of exception words or service words that will be found last if there are no other results.
++ High search speed. In the country of the hosting provider, the average request speed is 60 - 100 milliseconds. 
+  (In this case, there are 43 thousand cities in the database)
+  
+The code also comes with a function to create keywords from a string, which is target for search. Having keywords column in DB table makes search more efficient, because:
++ Saves time for processing the target string during the search.
++ Creates the possibility of adding new keywords by which the target string can be found without changing it.
++ Creates the possibility of excluding exception words (or service words).
+
+Search interface implemented using JavaScript, HTML, CSS. This demo is made in a minimalistic but functional design with a convenient mobile version. 
+The code also provides a JavaScript function for switching between the found results using the cursor.
+
+## Working demo
+https://www.search-city-info.online/
+
+## How to use
+1. **Using the search**
+In this example, the JavaScript file sends a fetch request with the search text and the "action" variable to the core.php file, which calls the necessary function
+in the function.php file according to the value in "action". This allows you to put different functions in the function.php file and call them independently.
+In this case, 2 functions are used: search as you type and search for information about the city when you click on one of the cities found.
+The search function always returns an object in the JavaScript file with the keys: results, text, keys. The "results" key corresponds to the results array, 
+"text" - the escaped text of the query is returned, keys - an array with keys that are similar to the query (they are used to highlight the match in the found text).
+This way you can use any kind of php requests and have any JavaScript file structure. You need to do: 
++ In function.php connect to the database by entering the hostname, login, password and database name.
++ Specify the correct path to the core.php file, send request: "serach text ", action: "name of the function".
++ Make sure you have keywords column in target table.(possible to search without keywords, but performance will be worse).
+
+2. **Creating keywords**
+In createKeywords.php you can find a function which slect a string from target column and divide it in single words which are separated by "+". 
+There is an array with exception or service words, which can be used to exclude unwanted words from keywords column. How to use the function(an example):
++ Open the createKeywords.php file and connect to the database by entering the hostname, login, password and database name.
++ Create a new column in target table with String type (make sure the length of the column value should be slightly more than target column).
++ Connect createKeywords.php to your project or insert the code from createKeywords.php to your file with .php extention and reload the page.
++ Note that the process may take some time depending on the number of items in the table.
++ Delete createKeywords.php code from your code or disconnect createKeywords.php
+
+### License
+MIT © Oleksandr Chernokolov - [BlackPrick](https://github.com/BlackPrick).