PHP Basics

21. What is use of in_array() function in php ?  

in_array used to checks if a value exists in an array

22. Is multiple inheritance supported in PHP?  

PHP includes only single inheritance, it means that a class can be extended from only one single class using the keyword 'extended'.

23. What is the meaning of a final class and a final method?  

'final' is introduced in PHP5. Final class means that this class cannot be extended and a final method cannot be overrided.

24. How comparison of objects is done in PHP5?  

We use the operator '==' to test is two object are instanced from the same class and have same attributes and equal values. We can test if two object are refering to the same instance of the same class by the use of the identity operator '==='.

25. How can PHP and HTML interact?  

It is possible to generate HTML through PHP scripts, and it is possible to pass informations from HTML to PHP.

26. What type of operation is needed when passing values through a form or an URL?  

If we would like to pass values througn a form or an URL then we need to encode and to decode them using htmlspecialchars() and urlencode().

27. How can PHP and Javascript interact?  

PHP and Javascript cannot directly interacts since PHP is a server side language and Javascript is a client side language. However we can exchange variables since PHP is able to generate Javascript code to be executed by the browser and it is possible to pass specific variables back to PHP via the URL.

28. What is needed to be able to use image function?  

GD library is needed to be able execute image functions.

29. What is the use of the function 'imagetypes()'?  

imagetypes() gives the image format and types supported by the current version of GD-PHP.

30. What are the functions to be used to get the image's properties (size, width and height)?  

The functions are getimagesize() for size, imagesx() for width and imagesy() for height.

31. How failures in execution are handled with include() and require() functions?  

If the function require() cannot access to the file then it ends with a fatal error. However, the include() function gives a warning and the PHP script continues to execute.

32. What is the main difference between require() and require_once()?  

require() and require_once() perform the same task except that the second function checks if the PHP script is already included or not before executing it.

33. How can we display information of a variable and readable by human with PHP?  

To be able to display a human-readable result we use print_r().

34. How is it possible to set an infinite execution time for PHP script?  

The set_time_limit(0) added at the beginning of a script sets to infinite the time of execution to not have the PHP error 'maximum execution time exceeded'.It is also possible to specify this in the php.ini file.

35. What does the PHP error 'Parse error in PHP - unexpected T_variable at line x' means?  

This is a PHP syntax error expressing that a mistake at the line x stops parsing and executing the program.

36. What should we do to be able to export data into an Excel file?  

The most common and used way is to get data into a format supported by Excel. For example, it is possible to write a .csv file, to choose for example comma as separator between fields and then to open the file with Excel.

37. What is the function file_get_contents() useful for?  

file_get_contents() lets reading a file and storing it in a string variable.

38. What is the function mysql_pconnect() useful for?  

mysql_pconnect() ensure a persistent connection to the database, it means that the connection do not close when the the PHP script ends.

39. How the result set of Mysql be handled in PHP?  

The result set can be handled using mysql_fetch_array, mysql_fetch_assoc, mysql_fetch_object or mysql_fetch_row.

40. How is it possible to know the number of rows returned in result set?  

The function mysql_num_rows() returns the number of rows in a result set.

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