In this blog we are continuing the learning of PHP with more questions and answers that will be enhancing the skill of developers for the PHP
How to initiate a session in PHP? : The use of the function session_start() lets us activating a session.
How can you propagate a session id? : You can propagate a session id via cookies or URL parameters.
What is the meaning of a Persistent Cookie? : A persistent cookie is permanently stored in a cookie file on the browser’s computer. By default, cookies are temporary and are erased if we close the browser.
When do sessions end? : Sessions automatically end when the PHP script finishes executing but can be manually ended using the session_write_close().
What is the difference between session_unregister() and session_unset()? : The session_unregister() function unregister a global variable from the current session and the session_unset() function frees all session variables.
What does $GLOBALS mean? : $GLOBALS is associative array including references to all variables which are currently defined in the global scope of the script.
What does $_SERVER mean? : $_SERVER is an array including information created by the web server such as paths, headers, and script locations.
What does $_FILES means? : $_FILES is an associative array composed of items sent to the current script via the HTTP POST method.
What is the difference between $_FILES[‘userfile’][‘name’] and $_FILES[‘userfile’][‘tmp_name’]? : $_FILES[‘userfile’][‘name’] represents the original name of the file on the client machine, $_FILES[‘userfile’][‘tmp_name’] represents the temporary filename of the file stored on the server.
How can we get the error when there is a problem to upload a file? : $_FILES[‘userfile’][‘error’] contains the error code associated with the uploaded file.
How can we change the maximum size of the files to be uploaded? : We can change the maximum size of files to be uploaded by changing upload_max_filesize in php.ini.
What does $_ENV mean? : $_ENV is an associative array of variables sent to the current PHP script via the environment method.
What does $_COOKIE mean? : $_COOKIE is an associative array of variables sent to the current PHP script using the HTTP Cookies.
What does the scope of variables mean? : The scope of a variable is the context within which it is defined. For the most part, all PHP variables only have a single scope. This single scope spans included and required files as well.
what the difference between the ‘BITWISE AND’ operator and the ‘LOGICAL AND’ operator? : $a and $b: TRUE if both $a and $b are TRUE. $a & $b: Bits that are set in both $a and $b are set.
What are the two main string operators? : The first is the concatenation operator (‘.’), which returns the concatenation of its right and left arguments. The second is (‘.=’), which appends the argument on the right to the argument on the left.
What is the differences between $a != $b and $a !== $b? : != means inequality (TRUE if $a is not equal to $b) and !== means non-identity (TRUE if $a is not identical to $b).
How can we determine whether a PHP variable is an instantiated object of a certain class? : To be able to verify whether a PHP variable is an instantiated object of a certain class we use instanceof.
What is the goto statement useful for? : The goto statement can be placed to enable jumping inside the PHP program. The target is pointed by a label followed by a colon, and the instruction is specified as a goto statement followed by the desired target label.
What is the difference between Exception::getMessage and Exception:: getLine? : Exception::getMessage lets us getting the Exception message and Exception::getLine lets us getting the line in which the exception occurred.
What does the expression Exception::__toString means? : Exception::__toString gives the String representation of the exception.
How is it possible to parse a configuration file? : The function parse_ini_file() enables us to load in the ini file specified in filename and returns the settings in it in an associative array.
How can we determine whether a variable is set? : The boolean function isset determines if a variable is set and is not NULL.
What is the difference between the functions strstr() and stristr()? : The string function strstr(string allString, string occ) returns part of allString from the first occurrence of occ to the end of allString. This function is case sensitive. stristr() is identical to strstr() except that it is case insensitive.
What is the difference between for and foreach? : for is expressed as follows: for (expr1; expr2; expr3) statement: The first expression is executed once at the beginning. In each iteration, expr2 is evaluated. If it is TRUE, the loop continues, and the statements inside for are executed. If it evaluates to FALSE, the execution of the loop ends. expr3 is tested at the end of each iteration. However, foreach provides an easy way to iterate over arrays, and it is only used with arrays and objects.
