Impelsys Interview Questions, Process, and Tips

There are three types of errors in PHP: syntax errors, runtime errors, and logical errors.

• Syntax errors occur when the code violates the rules of PHP syntax.

• Runtime errors occur during the execution of the script, such as division by zero or accessing undefined variables.

• Logical errors do not cause the script to terminate, but they produce incorrect results or unexpected behavior.

An autoloader is a function that automatically loads classes when they are needed in a PHP script.

• Autoloaders eliminate the need to manually include class files.

• They use naming conventions to locate and load class files.

• Autoloaders can be registered using spl_autoload_register() function.

• Composer provides a default autoloader for PHP projects.

Abstract classes and interfaces are used to define common methods and properties for classes to implement.

• Abstract classes cannot be instantiated and can contain both abstract and non-abstract methods.

• Interfaces only contain method signatures and constants, and classes can implement multiple interfaces.

• Abstract classes are useful for creating a base class with common functionality, while interfaces are useful for defin...read more

The .htaccess file is used to configure web server settings for a specific directory.

• Used to set up redirects and rewrite rules

• Can restrict access to certain files or directories

• Can set custom error pages

• Can enable/disable certain features like caching or compression

I follow PSR coding standards and adhere to best practices.

• I follow PSR-1 and PSR-2 coding standards.

• I use meaningful variable and function names.

• I write clean and readable code.

• I use proper indentation and spacing.

• I avoid using global variables.

• I use comments to explain complex code.

• I adhere to best practices for security and performance.

• For example, I always use prepared statements to prevent SQL injection attacks.

DBMS normalisation and keys

• Normalization is the process of organizing data in a database to reduce redundancy and dependency

• Keys are used to uniquely identify a record in a table

• Primary key is a unique identifier for a record

• Foreign key is a field in a table that refers to the primary key of another table

• Composite key is a combination of two or more fields that uniquely identify a record

Distinct returns unique values while group by groups and aggregates data based on a column.

• Distinct returns only unique values from a single column.

• Group by groups and aggregates data based on a column.

• Distinct can be used to count the number of unique values in a column.

• Group by can be used to group data by a column and perform aggregate functions like sum, count, avg, etc.

• Distinct is used to remove duplicates from a ...read more

Right join and right outer join are the same thing.

• Right join and right outer join are interchangeable terms.

• Both return all the rows from the right table and matching rows from the left table.

• If there is no match, the result will contain NULL values for the left table columns.

• Used to combine data from two tables based on a common column.

• Syntax: SELECT * FROM table1 RIGHT JOIN table2 ON table1.column = table2.column;

Special characters in columns can be handled by replacing or removing them.

• Identify the special characters in the column

• Replace the special characters with a suitable alternative

• Remove the special characters if they are not necessary

• Use regular expressions to handle complex special characters

• Ensure that the data type of the column is appropriate