In PHP, constant identifiers are always case-insensitive. It means that you can access a constant using any case (uppercase or lowercase) regardless of how it was defined. For example, if a constant is defined as "CONSTANT_NAME", you can access it as "constant_name" or "CoNsTaNt_NaMe". This behavior ensures that constants can be used consistently regardless of the case sensitivity. Learn more: https://www.php.net/manual/en/language.constants.php

In the context of PHP, OOP stands for Object-Oriented Programming. It is a programming paradigm that focuses on creating objects and defining their behavior using classes, inheritance, encapsulation, and polymorphism. The correct option is "Object-Oriented Programming." For further details, refer to the PHP documentation on object-oriented programming: http://php.net/manual/en/language.oop5.php

The + operator in PHP is used for addition. It can be used to add two numbers or concatenate two strings. When used with numbers, it performs mathematical addition, while with strings, it concatenates them. For example, $sum = $num1 + $num2; will add the values of $num1 and $num2 and store the result in $sum. Similarly, $fullName = $firstName + $lastName; will concatenate the values of $firstName and $lastName to form a full name. Learn more: https://www.php.net/manual/en/language.operators.arithmetic.php

The 'BITWISE AND' operator (&) performs bitwise comparison of individual bits in two operands, while the 'LOGICAL AND' operator (&&) performs logical comparison of two Boolean expressions. Learn more: http://php.net/manual/en/language.operators.bitwise.php

The do...while loop in PHP tests the condition after executing the block of code. The code block is executed at least once, and then the condition is checked. If the condition evaluates to true, the loop will repeat. If the condition evaluates to false, the loop will terminate. The do...while loop guarantees that the code block is executed at least once, regardless of the condition. It is useful when you want to ensure the execution of a specific code block before checking the condition for further iterations. Learn more: https://www.php.net/manual/en/control-structures.do.while.php

True. In a PHP associative array, you can use numerical keys, along with string keys, to associate specific values. While string keys are commonly used for associative arrays, numerical keys can also be employed when they are suitable for organizing and accessing the elements in the array. The keys in an associative array provide flexibility in data retrieval and allow for a variety of use cases in PHP programming. Learn more: https://www.php.net/manual/en/language.types.array.php#language.types.array.syntax

The correct option is 4. Multidimensional arrays in PHP have various common uses. They are commonly used for representing tabular data, such as spreadsheet-like structures, where rows and columns are organized into a multidimensional array. Multidimensional arrays are also useful for storing form input data, allowing easy access to different fields and values. Additionally, they are employed for managing hierarchical data relationships, such as representing nested categories or tree-like structures. The flexibility of multidimensional arrays allows for efficient data organization and manipulation in these scenarios. Learn more: https://www.php.net/manual/en/language.types.array.php#language.types.array.syntax

PHP is indeed case-sensitive for variable names. This means that $var and $Var would be considered two separate variables. On the other hand, PHP function names are not case-sensitive. This is one of the many aspects that can make PHP tricky for beginners. Learn more: https://www.php.net/manual/en/language.variables.basics.php

The while loop in PHP will continue to execute a block of code as long as the specified condition is true. The condition is checked before each iteration of the loop. If the condition evaluates to true, the block of code is executed, and then the condition is checked again for the next iteration. If the condition evaluates to false, the loop terminates, and the execution continues with the code following the loop. The while loop is useful when you don't know the exact number of iterations in advance, but you want to repeat a block of code based on a specific condition. Learn more: https://www.php.net/manual/en/control-structures.while.php

The $_SESSION superglobal array in PHP is used to access session variables. It is a predefined superglobal array that allows you to store and retrieve data across multiple pages or requests within the same session. The values stored in $_SESSION are specific to each individual user session. For further information, visit: http://php.net/manual/en/reserved.variables.session.php