In PHP, there are two types of comment syntax. The first type, //, is for single-line comments. The second type, /.../, is for multiple-line comments. HTML-style comments (< !--...-- >) are not recognized by PHP. So, both /* Comment */ and // Comment are valid ways to denote a comment in PHP. Learn more: https://www.php.net/manual/en/language.basic-syntax.comments.php

In PHP, $_SERVER is an array that contains server information, such as headers, paths, and script locations. It is a superglobal variable accessible from anywhere in the PHP script. Learn more: http://php.net/manual/en/reserved.variables.server.php

The statement is true. The $_POST superglobal is commonly used to collect form data submitted via the POST method. When an HTML form is submitted with the POST method, the form data is sent in the body of the HTTP request, and PHP populates the $_POST superglobal with the submitted values. This allows developers to access and process the form data securely. Learn more: https://www.php.net/manual/en/reserved.variables.post.php

To sort an associative array by its keys in PHP, you would use the ksort() function. The ksort() function arranges the elements of an associative array in ascending order based on their keys. The values associated with each key remain linked to their corresponding keys even after sorting. This function directly modifies the original associative array by rearranging its key-value pairs. Sorting an associative array by keys can be useful when you need to organize and retrieve data based on a specific key order. Learn more: https://www.php.net/manual/en/function.ksort.php

The elseif statement in PHP can be used to test multiple conditions. It allows you to specify a new condition to be checked if the preceding if condition is false. By using elseif, you can create a chain of conditions to be evaluated sequentially until a matching condition is found. This enables you to handle different scenarios and execute different code blocks based on different conditions. The elseif statement is a powerful tool for implementing complex decision-making logic in your PHP scripts. Learn more: https://www.php.net/manual/en/control-structures.elseif.php

To add the values of two variables in PHP, you would use the + operator. The expression $sum = $var1 + $var2; will add the values of $var1 and $var2 and store the result in the variable $sum. The + operator is the arithmetic addition operator in PHP and is used to perform addition operations on numerical values. Learn more: https://www.php.net/manual/en/language.operators.arithmetic.php

The strlen() function in PHP can be used to find the length of a string. It returns the number of characters in a string. The count() function is used to count the number of elements in an array or an object. The size() and length() functions do not exist in PHP as built-in functions for finding the length of a string. Learn more: https://www.php.net/manual/en/function.strlen.php

The main purpose of a constructor in a PHP class is to initialize the object when it is created. The correct option is "object." The constructor is called automatically when an object is created from the class, allowing you to initialize its properties or perform other setup tasks. For more information, consult the PHP documentation on constructors: http://php.net/manual/en/language.oop5.decon.php

The strftime() function can be used to format a date and time according to a specified format string. For more information, refer to: http://php.net/manual/en/function.strftime.php

To encode a PHP array into a JSON object, you can use the json_encode() function. It converts a PHP value (such as an array) into its JSON representation. The other mentioned options (json_serialize(), json_convert()) are not valid PHP functions for encoding an array into a JSON object. For further details, refer to the PHP documentation on json_encode(): http://php.net/manual/en/function.json-encode.php