Core PHP Interview Questions

Core PHP Interview Questions Download Core PHP Interview Questions PDF

Core PHP Interview Questions

Path Traversal also is known as Directory Traversal is referring to an attack which is attacked by an attacker to read into the files of the web application. Also, he/she can reveal the content of the file outside the root directory of a web server or any application. Path traversal operates the web application file with the use of dot-dot-slash (../) sequences, as ../ is a cross-platform symbol to go up in the directory.

Path traversal basically implements by an attacker when he/she wants to gain secret passwords, access token or other information stored in the files. Path traversal attack allows the attacker to exploit vulnerabilities present in web file.

The mail function is used in PHP to send emails directly from script or website. It takes five parameters as an argument.

Syntax of mail (): mail (to, subject, message, headers, parameters);

  • to refers to the receiver of the email
  • Subject refers to the subject of an email
  • the message defines the content to be sent where each line separated with /n and also one line can't exceed 70 characters.
  • Headers refer to additional information like from, Cc, Bcc. These are optional.
  • Parameters refer to an additional parameter to the send mail program. It is also optional

You can access standard error stream in PHP by using following code snippet:

$stderr = fwrite("php://stderr");

$stderr = fopen("php://stderr", "w");

$stderr = STDERR;

In PHP both functions are used to find the first occurrence of substring in a string except
stristr() is case-insensitive and strstr is case-sensitive,if no match is found then FALSE will be returned.

Sample Usage:

$email = ‘’;
$hostname = strstr($email, ‘@’);
echo $hostname;
stristr() does the same thing in Case-insensitive manner

There are 13 types of errors in PHP, We have listed all below

  • E_ERROR: A fatal error that causes script termination.
  • E_WARNING: Run-time warning that does not cause script termination.
  • E_PARSE: Compile time parse error.
  • E_NOTICE: Run time notice caused due to error in code.
  • E_CORE_ERROR: Fatal errors that occur during PHP initial startup.
  • E_CORE_WARNING: Warnings that occur during PHP initial startup.
  • E_COMPILE_ERROR: Fatal compile-time errors indication problem with script.
  • E_USER_ERROR: User-generated error message.
  • E_USER_WARNING: User-generated warning message.
  • E_USER_NOTICE: User-generated notice message.
  • E_STRICT: Run-time notices.
  • E_RECOVERABLE_ERROR: Catchable fatal error indicating a dangerous error
  • E_ALL: Catches all errors and warnings.

Calculating days between two dates in PHP

$date1 = date('Y-m-d');
$date2 = '2015-10-2';
$days = (strtotime($date1)-strtotime($date2))/(60*60*24);
echo $days;

Both are used to make the changes to your PHP setting. These are explained below:

php.ini: It is a special file in PHP where you make changes to your PHP settings. It works when you run PHP as CGI. It depends on you whether you want to use the default settings or changes the setting by editing a php.ini file or, making a new text file and save it as php.ini.

.htaccess: It is a special file that you can use to manage/change the behavior of your site. It works when PHP is installed as an Apache module. These changes include such as redirecting your domain’s page to https or www, directing all users to one page, etc.

A database provides more flexibility and reliability than does logging to a file. It is easy to run queries on databases and generate statistics than it is for flat files. Writing to a file has more overhead and will cause your code to block or fail in the event that a file is unavailable. Inconsistencies caused by slow replication in AFS may also pose a problem to errors logged to files. If you have access to MySQL, use a database for logs, and when the database is unreachable, have your script automatically send an e-mail to the site administrator.

To terminate the script in PHP, exit() function is used. It is an inbuilt function which outputs a message and then terminates the current script. The message which is you want to display is passed as a parameter to the exit () function and this function terminates the script after displaying the message. It is an alias function of die () function. It doesn’t return any value.

Syntax: exit(message)

Where massage is a parameter to be passed as an argument. It defines message or status.

Exceptions of exit():

  • If no status is passed to exit(), then it can be called without parenthesis.
  • If a passed status is an integer then the value will not be printed but used as the exit status.
  • The range of exit status is from 0 to 254 where 255 is reserved in PHP.

Errors And Exceptions

  • exit() can be called without parentheses if no status is passed to it. Exit() function is also known by the term language construct.
  • If the status passed to an exit() is an integer as a parameter, that value will be used as the exit status and not be displayed.
  • The range of exit status should be in between 0 to 25. the exit status 255 should not be used because it is reserved by PHP.


Difference between echo and print in PHP

echo in PHP

  • echo is language constructs that display strings.
  • echo has a void return type.
  • echo can take multiple parameters separated by comma.
  • echo is slightly faster than print.

Print in PHP

  • print is language constructs that display strings.
  • print has a return value of 1 so it can be used in expressions.
  • print cannot take multiple parameters.
  • print is slower than echo.

It is easy and simple to execute PHP scripts from the windows command prompt. You just follow the below steps:

1. Open the command prompt. Click on Start button->Command Prompt.

2. In the Command Prompt, write the full path to the PHP executable(php.exe) which is followed by the full path of a script that you want to execute. You must add space in between each component. It means to navigate the command to your script location.

For example,

let you have placed PHP in C:\PHP, and your script is in C:\PHP\sample-php-script.php,

then your command line will be:

C:\PHP\php.exe C:\PHP\sample-php-script.php

3. Press the enter key and your script will execute.

PHP: Hypertext Preprocessor is open source server-side scripting language that is widely used for creation of dynamic web applications.It was developed by Rasmus Lerdorf also know as Father of PHP in 1994.

PHP is a loosely typed language , we didn’t have to tell PHP which kind of Datatype a Variable is. PHP automatically converts the variable to the correct datatype , depending on its value.

There are many differences between PHP 5 and 7. Some of the main points are:

  • Performance: it is obvious that later versions are always better than the previous versions if they are stable. So, if you execute code in both versions, you will find the performance of PHP 7 is better than PHP5. This is because PHP 5 use Zend II and PHP & uses the latest model PHP-NG or Next Generation.
  • Return Type: In PHP 5, the programmer is not allowed to define the type of return value of a function which is the major drawback. But in PHP 7, this limitation is overcome and a programmer is allowed to define the return type of any function.
  • Error handling: In PHP 5, there is high difficulty to manage fatal errors but in PHP 7, some major errors are replaced by exceptions which can be managed effortlessly. In PHP 7, the new engine Exception Objects has been introduced.
  • 64-bit support: PHP 5 doesn’t support 64-bit integer while PHP 7 supports native 64-bit integers as well as large files.
  • Anonymous Class: Anonymous class is not present n PHP 5 but present in PHP 7. It is basically used when you need to execute the class only once to increase the execution time.
  • New Operators: Some new operators have added in PHP 7 such as <=> which is called a three-way comparison operator. Another operator has added is a null coalescing operator which symbol as?? and use to find whether something exists or not.
  • Group Use declaration: PHP 7 includes this feature whereas PHP 5 doesn’t have this feature.