In PHP, Regular Expressions are sequences of characters that form a search pattern, used mainly for text manipulation. Regular expressions provide a powerful and flexible way to search, match, and manipulate strings based on specific patterns. They can be used for tasks such as validating inputs, extracting data, performing string substitutions, and more. Regular expressions enable developers to define complex search patterns and apply them to strings, making it easier to work with textual data. Learn more: https://www.php.net/manual/en/book.regex.php

The if statement in PHP executes a block of code if a condition is true. It allows you to test a condition and execute code based on the result. The if statement can handle both simple conditions and complex conditions involving logical operators. It can be used to test multiple conditions by using logical operators or by nesting if statements within each other. It is a fundamental control structure in PHP and is widely used for decision-making and flow control. Learn more: https://www.php.net/manual/en/control-structures.if.php

The == operator in PHP is a type of comparison operator. It is used to compare two values for equality. The == operator checks if the values on both sides are equal, regardless of their data types. For example, $num1 == $num2 will return true if $num1 is equal to $num2, and false otherwise. Learn more: https://www.php.net/manual/en/language.operators.comparison.php

The correct option is 1. To store information about a user session in PHP, you would use the $_SESSION superglobal. The $_SESSION superglobal is an associative array that allows you to store and access session variables. It is used to maintain session data across multiple page requests for a specific user. By storing data in $_SESSION, you can preserve user-specific information throughout their interaction with your web application. The session data is stored on the server and can be accessed across different pages or scripts as long as the session is active. Learn more: https://www.php.net/manual/en/reserved.variables.session.php

This statement is true. In PHP, strings can be defined using either single quotes ('') or double quotes (""). Both single quotes and double quotes are used to delimit string literals. The choice between single quotes and double quotes depends on the specific requirements and whether variable interpolation or escape sequences are needed. Learn more: https://www.php.net/manual/en/language.types.string.php

To read data from an InputStream object connected to a socket, you typically use the read() method. This method reads a single byte of data and returns an integer representation of that byte. You can then cast it to the appropriate data type. The other options are not standard methods for reading from sockets.

In Java, when you define a new exception by extending an existing exception class, it's called "Customization of exception." This process allows you to create your own exception classes that suit your application's specific needs while maintaining compatibility with Java's exception hierarchy.

The Serializable interface in Java does not contain any methods. Instead, it serves as a marker interface, indicating that the class implementing it can be serialized. Serialization allows objects to be converted into a byte stream for storage or transmission. It's used for objects that need to be saved to a file or sent over a network.

Merge Sort has a space complexity of O(n) because it creates a temporary array to hold the merged subarrays during the sorting process. Unlike some other sorting algorithms like Quick Sort, Merge Sort does not use a constant amount of extra memory (O(1)) or divide the memory usage logarithmically (O(log n)).

In Java, you can use the static valueOf method of the Integer class to obtain a string representation of a primitive data type. For example, Integer.valueOf(42) will return the string "42". The other options do not provide this specific functionality.

In Java, the commonly used class for reading characters from a file is FileReader. It is part of the java.io package and is specifically designed for character input. Other options like FileWriter, FileInputReader, and FileOutputReader are not standard classes in Java for file reading.

The correct answer is getPort(). In Java, the URL class provides the getPort() method, which allows you to obtain the port number of a URL. This is useful when working with network-related tasks where you need to know the port associated with a particular URL.