Advanced PHP Interview Questions and Answers

Answer:

PHP is a general-purpose scripting language, mostly implemented in C and C++, and is often used in web development. It is a highly performant language as the code need not be compiled before execution. It is also free and open-sourced, and can be easily learned. PHP is also cost-effective as most web hosting servers support it by default.

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PEAR is a framework and repository for reusable PHP components. PEAR stands for PHP Extension and Application Repository. It contains all types of PHP code snippets and libraries.

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Cookies store data about a user on the browser. It is used to identify a user and is embedded on the user’s computer when they request a particular page. We can create cookies in PHP using the setcookie() function.

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Both of them are used for making changes to the PHP settings.

• .htaccess – A special file that can be used to change or manage the behavior of a website. Directing all users to one page and redirecting the domain’s page to https or www are two of the most important uses of the file. For .htaccess to work, PHP needs to be installed as an Apache module.
• ini – This special file allows making changes to the default PHP settings. Either the default php.ini file can be edited, or a new file can be created with relevant additions and then saved as the php.ini file. For php.ini to work, PHP needs to run as CGI.

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The name of the output type needs to be specified in parentheses before the variable that is to be cast.

Some examples are:

(array): casts to array

(bool), (boolean): casts to Boolean

(double), (float), (real): casts to float

(int), (integer): casts to integer

(object): casts to object

(string): casts to string

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Constructors and destructors in PHP are special types of functions, which are automatically called when a PHP class object is created and destroyed, respectively.

While a constructor is used to initialize the private variables of a class, a destructor frees the resources created or used by the class.

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PHP supports three types of errors:

Notices: Errors that are non-critical. These occur during the script execution. Accessing an undefined variable is an instance of a notice.

Warnings: Errors that have a higher priority than notices. Like with notices, the execution of a script containing Warnings remains uninterrupted. An example of a notice includes a file that doesn’t exist.

Fatal Error: A termination in the script execution results as soon as such an error is encountered. Accessing a property of a non-existing object yields a fatal error.

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The traits mechanism allows for the creation of reusable code in PHP-like languages where there is no support for multiple inheritances. A trait can’t be instantiated on its own.

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The PHP parsing engine must be able to distinguish PHP code from other page elements. The mechanism to achieve this is called ‘escaping to PHP’.

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Three types of an array are present in PHP:

• Indexed array, which is an array with a numeric key.
• An associative array is where each key has its specific value.
• A multidimensional array contains one or more arrays within itself.

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GET, and POST are two of the most basic methods used in web communication between a server and a client. GET is a type of request that asks a server to send back a resource, while POST is a type of request that sends data to a server.

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A callback is a PHP function used to execute other parts, and it is often used to add custom functionality to the code or to provide an alternative way to execute code.

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Runtime exceptions occur during the execution of code and are caused by unexpected events, such as attempting to access an array index that does not exist. Compile-time exceptions, on the other hand, occur before the execution of code and are usually caused by code that does not compile correctly, such as syntax errors or attempting to use an undeclared variable.

Answer:

There are two statements for getting output in PHP — echo and print. The distinctions between the two are:

• Although used rarely, echo has the ability to take multiple parameters. The print statement, on the contrary, can accept only a single argument.
• Echo has no return value whereas print has a return value of 1. Hence, the latter is the go-to option for use in expressions.
• Generally, the echo statement is preferred over the print statement as it is slightly faster.

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Yes, it is possible to extend the execution time of a PHP script. We have the set_time_limit(int seconds) function for that. You need to specify the duration, in seconds, for which you wish to extend the execution time of a PHP script. The default time is 30 seconds.

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PHP parameterized functions are functions with parameters. You can pass any number of parameters inside a function. These given parameters act as variables inside your function. They are specified inside the parentheses, after the function name. Output depends upon dynamic values passed as parameters into the function.

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Following are the key differences between them:

• The for loop is considered to be openly executing the iteration whereas the foreach loop hides the iteration and visibly simplified.
• The performance of foreach loop is considered better in comparison with for loop.
• The foreach loop though iterates over an array of elements, the execution is simplified and finish the loop in less time comparing with for loop.
• The foreach loop allocates temporary memory for index iterations which makes the overall system redundant its performance in terms of memory allocation.

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The Include() function is used to put data of one PHP file into another PHP file. If errors occur, then the include() function produces a warning but does not stop the execution of the script, and it will continue to execute.

The Require() function is also used to put data of one PHP file to another PHP file. If there are any errors, then the require() function produces a warning and a fatal error and stops the script.

Answer:

The necessary steps to create a MySQL database using PHP are:

• Establish a connection to MySQL server from your PHP script.
• If the connection is successful, write a SQL query to create a database and store it in a string variable.
• Execute the query.

Answer:

Memcached is an effective caching daemon designed specifically for decreasing database load in dynamic web applications. Memcache module offers a handy procedural and object-oriented interface to Memcached.

Memcache is a memory storage space, and it is possible to run Memcache on a single or several servers. Hence, it is possible to share a single instance of Memcache between multiple projects.

It is possible to configure a client to speak to a distinct set of instances. Therefore, running two different Memcache processes on the same host is also allowed. Despite running on the same host, both such processes stay independent, unless there is a partition of data.