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Welcome !!!. In this section we are providing you some frequently asked PHP Interview Questions which will help you to win interview session easily. Candidates must read this section,Then by heart the questions and answers. Also, review sample answers and advice on how to answer these typical interview questions. PHP is an important part of the web world, and every web developer should have the basic knowledge in PHP.Common PHP interview questions, which should help you become a best PHP codder. We hope you find these questions useful. If you are an interviewer, Take the time to read the common interview questions you will most likely be asked.

1. What is PHP?                                                                                                                            PHP is a server side scripting language commonly used for web applications. PHP has many frameworks and cms for creating websites.Even a non technical person can cretae sites using its CMS.WordPress,osCommerce are the famus CMS of php.It is also an object oriented programming language like java,C-sharp etc.It is very eazy for learning
   
   
2. What is the use of "echo" in php?                                                                                               It is used to print a data in the webpage, Example: <?php echo 'Car insurance'; ?> , The following code print the text in the webpage
   
   
3. How to include a file to a php page?                                                                                         We can include a file using "include() " or "require()" function with file path as its parameter.
   
   
4. What's the difference between include and require?                                                                 If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
   
5. require_once(), require(), include().What is difference between them?                                    require() includes and evaluates a specific file, while require_once() does that only if it has not been included before (on the same page). So, require_once() is recommended to use when you want to include a file where you have a lot of functions for example. This way you make sure you don't include the file more times and you will not get the "function re-declared" error.
   
   
6. Differences between GET and POST methods ?                                                                    We can send 1024 bytes using GET method but POST method can transfer large amount of data and POST is the secure method than GET method .
   
   
7. How to declare an array in php?                                                                                                       Eg : var $arr = array('apple', 'grape', 'lemon');
   
   
8. What is the use of 'print' in php?                                                                                           This is not actually a real function, It is a language construct. So you can use with out parentheses with its argument list.
   
   Example print('PHP Interview questions');
   print 'Job Interview ');
   
   
9. What is use of in_array() function in php ?                                                                                      in_array used to checks if a value exists in an array
   
   
10. What is use of count() function in php ?                                                                                     count() is used to count all elements in an array, or something in an object
    
    
11. What's the difference between include and require?                                                               It's how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
    
    
12. What is the difference between Session and Cookie?                                                            The main difference between sessions and cookies is that sessions are stored on the server, and cookies are stored on the user's computers in the text file format. Cookies can't hold multiple variable while session can hold multiple variables..We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking
    
13. How to set cookies in PHP? 
     Setcookie("sample", "ram", time()+3600);
    
    
14. How to Retrieve a Cookie Value?                                                                                                eg : echo $_COOKIE["user"];
    
    
15. How to create a session? How to set a value in session ? How to Remove data from a session?                                                                                                                                            Create session : session_start();
    Set value into session : $_SESSION['USER_ID']=1;
    Remove data from a session : unset($_SESSION['USER_ID'];.
    
    
16. what types of loops exist in php? 
     for,while,do while and foreach (NB: You should learn its usage)
    
    
17. Note:-
    MySQLi (the "i" stands for improved) and PDO (PHP Data Objects) are the MySQL extensions used to connect to the MySQL server in PHP5 or verions, MySQL extension was deprecated in 2012.
    MySQLi only works with MySQL databases whereas PDO will works with 12 other Database systems
    I recommend PDO because, if you want to choose another database instead of MySQL, then you only have to change the connection string and a few queries. But if you are using MySQLi you will need to rewrite the entire code
    
    
18. How to create a mysql connection?

    Example (PDO)

    <?php
    $servername = "localhost";
    $username = "username";
    $password = "password";
    
    try {
        $conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
        // set the PDO error mode to exception    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        echo "Connected successfully";
        }
    catch(PDOException $e)
        {
        echo "Connection failed: " . $e->getMessage();
        }
    ?>

    
    

    Example (MySQLi Object-Oriented)

    <?php
    $servername = "localhost";
    $username = "username";
    $password = "password";
    $dbname = "myDB"; // Optional
    
    // Create connection$conn = new mysqli($servername, $username, $password, $dbname);
    
    // Check connection if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }
    echo "Connected successfully";
    ?>

    
    

    Example (MySQLi Procedural)

    <?php
    $servername = "localhost";
    $username = "username";
    $password = "password";
    $dbname = "myDB"; // Optional
    
    
    // Create connection $conn = mysqli_connect($servername, $username, $password, $dbname);
    
    // Check connection if (!$conn) {
        die("Connection failed: " . mysqli_connect_error());
    }
    echo "Connected successfully";
    ?>

    
    
19. How to execute an sql query? How to fetch its result ?

    Example (MySQLi Object-oriented)

    
    $sql = "SELECT id, firstname, lastname FROM MyGuests";
    $result = $conn->query($sql); // execute sql query
    
    if ($result->num_rows > 0) {
        // output data of each row
        while($row = $result->fetch_assoc()) { // fetch data from the result set
            echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
        }
    } else {
        echo "0 results";
    }
    
    

    Example (MySQLi Procedural)

    
    $sql = "SELECT id, firstname, lastname FROM MyGuests";
    $result = mysqli_query($conn, $sql); // execute sql query
    
    if (mysqli_num_rows($result) > 0) {
        // output data of each row
        while($row = mysqli_fetch_assoc($result)) { // fetch data from the result set
            echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
        }
    } else {
        echo "0 results";
    }
    

    Example (PDO)

    
    

    Method 1:USE PDO query method

    $stmt = $db->query('SELECT id FROM Employee');  
    $row_count = $stmt->rowCount();  
    echo $row_count.' rows selected';

    
    

    Method 2: Statements With Parameters

    $stmt = $db->prepare("SELECT id FROM Employee WHERE name=?");  
    $stmt->execute(array($name));  
    $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

20. Write a program using while loop
    <?php
    $x = 1;
    
    while($x <= 5) {
        echo "The number is: $x <br>";
        $x++;
    }
    ?>
21. How we can retrieve the data in the result set of MySQL using PHP?

    MySQLi methods

    • 1. mysqli_fetch_row
    • 2. mysqli_fetch_array
    • 3. mysqli_fetch_object
    • 4. mysqli_fetch_assoc

    PDO methods

    • 1. PDOStatement::fetch(PDO::FETCH_ASSOC)
    • 2. PDOStatement::fetch(PDO::FETCH_OBJ)
    • 3. PDOStatement::fetch()
    • 4. PDOStatement::fetch(PDO::FETCH_NUM).
    •  
22. What is the use of explode() function ? Syntax : array explode ( string $delimiter , string $string [, int $limit ] );
    This function breaks a string into an array. Each of the array elements is a substring of string formed by splitting it on boundaries formed by the string delimiter.
    
    
23. What is the difference between explode() and str_split() functions? str_split function splits string into array by regular expression. Explode splits a string into array by string.
    
24. What is the use of mysql_real_escape_string() function? It is used to escapes special characters in a string for use in an SQL statement
    
    
25. Write down the code for save an uploaded file in php.
    <?php
    if ($_FILES["file"]["error"] == 0)
    {
    move_uploaded_file($_FILES["file"]["tmp_name"],
          "upload/" . $_FILES["file"]["name"]);
          echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
    }
    ?>
26. How to create a text file in php?
    <?php
    $filename = "/home/user/guest/newfile.txt";
    $file = fopen( $filename, "w" );
    if( $file == false )
    {
    echo ( "Error in opening new file" ); exit();
    }
    fwrite( $file, "This is a simple test\n" );
    fclose( $file );
    ?>
27. How to strip whitespace (or other characters) from the beginning and end of a string ? The trim() function removes whitespaces or other predefined characters from both sides of a string.
    
28. What is the use of header() function in php ? 
     The header() function sends a raw HTTP header to a client browser.Remember that this function must be called before sending the actual out put.For example, You do not print any HTML element before using this function.

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