How a Google Search Works in Only Half a Second [VIDEO]

How a Google Search Works in Only Half a Second [VIDEO].

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What is a Session?

A session is a logical object created by the PHP engine to allow you to preserve data across subsequent HTTP requests.
There is only one session object available to your PHP scripts at any time. Data saved to the session by a script can be retrieved by the same script or another script when requested from the same visitor.
Sessions are commonly used to store temporary data to allow multiple PHP pages to offer a complete functional transaction for the same visitor

Difference between mysql_fetch_array(),mysql_fetch_row() and mysql_fetch_object()

mysql_fetch_array():: fetches a result row as a associated array, numeric array

mysql_fetch_row::fetches a result row as array

mysql_fetch_object: Fetaches a result row as object.

MySQL fetch object will collect first single matching record where mysql_fetch_array will collect all matching records from the table in an array
my fetch row fetch a result row as array

mysql_fetch_array ? Fetch a result row as an associative array, a numeric array, or both. Returns an array that corresponds to the fetched row and moves the internal data pointer ahead.

mysql_fetch_object ? Fetch a result row as an object. Returns an object with properties that correspond to the fetched row and moves the internal data pointer ahead.

mysql_fetch_row ? Get a result row as an enumerated array. Returns a numerical array that corresponds to the fetched row and moves the internal data pointer ahead.

PHP interview questions and answers

  1. What does a special set of tags <?= and ?> do in PHP? – The output is displayed directly to the browser.
  2. What’s the difference between include and require? – It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
  3. I am trying to assign a variable the value of 0123, but it keeps coming up with a different number, what’s the problem? – PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar PHP interview questions for more numeric problems.
  4. Would I use print "$a dollars" or "{$a} dollars" to print out the amount of dollars in this example? – In this example it wouldn’t matter, since the variable is all by itself, but if you were to print something like "{$a},000,000 mln dollars", then you definitely need to use the braces.
  5. How do you define a constant? – Via define() directive, like define ("MYCONSTANT", 100);
  6. How do you pass a variable by value? – Just like in C++, put an ampersand in front of it, like $a = &$b
  7. Will comparison of string "10" and integer 11 work in PHP? – Yes, internally PHP will cast everything to the integer type, so numbers 10 and 11 will be compared.
  8. When are you supposed to use endif to end the conditional statement? – When the original if was followed by : and then the code block without braces.
  9. Explain the ternary conditional operator in PHP? – Expression preceding the ? is evaluated, if it’s true, then the expression preceding the : is executed, otherwise, the expression following : is executed.
  10. How do I find out the number of parameters passed into function? – func_num_args() function returns the number of parameters passed in.
  11. If the variable $a is equal to 5 and variable $b is equal to character a, what’s the value of $$b? – 100, it’s a reference to existing variable.
  12. What’s the difference between accessing a class method via -> and via ::? – :: is allowed to access methods that can perform static operations, i.e. those, which do not require object initialization.
  13. Are objects passed by value or by reference? – Everything is passed by value.
  14. How do you call a constructor for a parent class? – parent::constructor($value)
  15. What’s the special meaning of __sleep and __wakeup? – __sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.
  16. Why doesn’t the following code print the newline properly?    <?php
                $str = ‘Hello, there.nHow are you?nThanks for visiting TechInterviews’;
                print $str;
        ?>
    Because inside the single quotes the n character is not interpreted as newline, just as a sequence of two characters – and n.
  17. Would you initialize your strings with single quotes or double quotes? – Since the data inside the single-quoted string is not parsed for variable substitution, it’s always a better idea speed-wise to initialize a string with single quotes, unless you specifically need variable substitution.
  18. How come the code <?php print "Contents: $arr[1]"; ?> works, but <?php print "Contents: $arr[1][2]"; ?> doesn’t for two-dimensional array of mine? – Any time you have an array with more than one dimension, complex parsing syntax is required. print "Contents: {$arr[1][2]}" would’ve worked.
  19. What is the difference between characters �23 and x23? – The first one is octal 23, the second is hex 23.
  20. With a heredoc syntax, do I get variable substitution inside the heredoc contents? – Yes.
  21. I want to combine two variables together:
     $var1 = 'Welcome to ';
     $var2 = 'TechInterviews.com';
    

    What will work faster? Code sample 1:

    $var 3 = $var1.$var2;
    

    Or code sample 2:

    $var3 = "$var1$var2";
    

    Both examples would provide the same result – $var3 equal to "Welcome to TechInterviews.com". However, Code Sample 1 will work significantly faster. Try it out with large sets of data (or via concatenating small sets a million times or so), and you will see that concatenation works significantly faster than variable substitution.

  22. For printing out strings, there are echo, print and printf. Explain the differences. – echo is the most primitive of them, and just outputs the contents following the construct to the screen. print is also a construct (so parentheses are optional when calling it), but it returns TRUE on successful output and FALSE if it was unable to print out the string. However, you can pass multiple parameters to echo, like:
     <?php echo 'Welcome ', 'to', ' ', 'TechInterviews!'; ?>

    and it will output the string "Welcome to TechInterviews!" print does not take multiple parameters. It is also generally argued that echo is faster, but usually the speed advantage is negligible, and might not be there for future versions of PHP. printf  is a function, not a construct, and allows such advantages as formatted output, but it’s the slowest way to print out data out of echo, print and printf.

  23. I am writing an application in PHP that outputs a printable version of driving directions. It contains some long sentences, and I am a neat freak, and would like to make sure that no line exceeds 50 characters. How do I accomplish that with PHP? – On large strings that need to be formatted according to some length specifications, use wordwrap() or chunk_split().
  24. What’s the output of the ucwords function in this example?
    	$formatted = ucwords("TECHINTERVIEWS IS COLLECTION OF INTERVIEW QUESTIONS");
    	print $formatted;

    What will be printed is TECHINTERVIEWS IS COLLECTION OF INTERVIEW QUESTIONS.
    ucwords() makes every first letter of every word capital, but it does not lower-case anything else. To avoid this, and get a properly formatted string, it’s worth using strtolower() first.

  25. What’s the difference between htmlentities() and htmlspecialchars()? – htmlspecialchars only takes care of <, >, single quote ‘, double quote " and ampersand. htmlentities translates all occurrences of character sequences that have different meaning in HTML.
  26. What’s the difference between md5(), crc32() and sha1() crypto on PHP? – The major difference is the length of the hash generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value. This is important when avoiding collisions.
  27. So if md5() generates the most secure hash, why would you ever use the less secure crc32() and sha1()? – Crypto usage in PHP is simple, but that doesn’t mean it’s free. First off, depending on the data that you’re encrypting, you might have reasons to store a 32-bit value in the database instead of the 160-bit value to save on space. Second, the more secure the crypto is, the longer is the computation time to deliver the hash value. A high volume site might be significantly slowed down, if frequent md5() generation is required.
  28. How do you match the character ^ at the beginning of the string? – ^^

http://www.techinterviews.com/php-interview-questions-and-answers

PHP cURL functions

cURL is a library which allows you to connect and communicate to many different types of servers with many different types of protocols. Using cURL you can:

Implement payment gateways’ payment notification scripts.
Download and upload files from remote servers.
Login to other websites and access members only sections.

PHP cURL library is definitely the odd man out. Unlike other PHP libraries where a whole plethora of functions is made available, PHP cURL wraps up a major parts of its functionality in just four functions.

A typical PHP cURL usage follows the following sequence of steps.

curl_init – Initializes the session and returns a cURL handle which can be passed to other cURL functions.

curl_opt – This is the main work horse of cURL library. This function is called multiple times and specifies what we want the cURL library to do.

curl_exec – Executes a cURL session.

curl_close – Closes the current cURL session.

Below are some examples which should make the working of cURL more clearer.

The below piece of PHP code uses cURL to download Google’s RSS feed.

As you can see, curl_setopt is the pivot around which the main cURL functionality revolves. cURL functioning is controlled by way of passing predefined options and values to this function.

The above code uses two such options.

CURLOPT_URL: Use it to specify the URL which you want to process. This could be the URL of the file you want to download or it could be the URL of the script to which you want to post some data.
CURLOPT_RETURNTRANSFER: Setting this option to 1 will cause the curl_exec function to return the contents instead of echoing them to the browser.

Source: http://www.phpinterviewquestion.com/

Superglobal variables in php.

There are number of superglobal variables in php

$GLOBALS
$_SERVER
$_GET
$_POST
$_FILES
$_COOKIE
$_SESSION
$_REQUEST
$_ENV

Source: http://www.phpinterviewquestion.com/

File reading/downloading using php.

This is the example, how to download pdf file using php. you can also use this code for zip file,word file,image file, any type of media file.

$filename=”directory/filename”;//In $filename will have to provide full path of file.

header(“Pragma: public”);

header(“Expires: 0″);

header(“Cache-Control: must-revalidate, post-check=0, pre-check=0″);

header(“Content-Type: application/force-download”);

header(“Content-Type: application/octet-stream”);

header(“Content-Type: application/download”);

header(“Content-Disposition: attachment; filename=”.basename($filename).”;”);

header(“Content-Transfer-Encoding: binary”);

header(“Content-type: application/pdf”);

header(“Content-Length: “.filesize($filename));

readfile(“$filename”);

exit();

If your file is pdf then use header(“Content-type: application/pdf”);

If zip file then use header(“Content-type: application/zip”);

In $filename provide full path of file.

Ex. If your file is in pdf folder and your php file is in outside of pdf folder.

Then $filename=”pdf/filename.pdf”;// will be.

If you want to display file not download, You have to remove below header from above code.

header(“Content-Disposition: attachment; filename=”.basename($filename).”;”);

Source: http://www.phpinterviewquestion.com/