Add Days to a Date

DATE Function in PHP - ADD DAYS
By using this function you can easily Add days into date and as well as subtract days from date.

//Example
$date = "2008-11-10";
$fdate = adddays($date,5);
echo fdate; //result : 2008-11-15

$date = "2008-11-10";
$fdate = adddays($date,-5);
echo fdate; //result : 2008-11-05


function adddays($date,$days){
$rs = $this->execute("select DATE_FORMAT(DATE_ADD('$date',INTERVAL $days DAY),'%Y-%m-%d') as newdate");
if($row = $this->row($rs)){
return $row["newdate"];
}else{
return "0000-00-00";
}
}
?>

Convert Date into SQL Date Format

In this function you can easily convert user input date format into SQL date format.
this 00/00/0000 to 0000-00-00

Example:
$date = "15/11/2008";
$query = "INSERT INTO TB VALUES('".tosqldate($date)."')";
// result: 2008-11-15


function tosqldate($strdata){
$strdata = trim($strdata);
if($strdata==""){
return "";
}
$arrdate = explode("/",$strdata);
if(count($arrdate) < 3){
return "";
}else{
return $arrdate[2]."-".$arrdate[1]."-".$arrdate[0];
}
}
?>

Chage Date Format

By use of this script or function you can easily change date format: this 2008-11-15 to 15/11/2008



// calling function
$date = "2008-11-15";
$fdate = formatdae($date);

echo $fdate; // Result: 15/11/2008

function formatdate($mysql_stamp,$type=1)
{
//$type = 1 date + time
//$type = 2 date
//$type = 3 time
// split mysql DATETIME stamp into date and time
if($mysql_stamp==""){
return "";
}
@list($date, $time) = split ('[ ]', $mysql_stamp);
@list($year, $month, $day) = split ('[-]', $date);
if( isset($time) && $time != "" )
{
list($hour, $minute, $second) = split ('[:]', $time);
if($hour>=12)
{
$ext = "PM";
$hour = $hour - 12;
}
else
{
$ext = "AM";
}
$time = " ".$hour.":".$minute." ".$ext;
}
else
{
$hour="";
$minute= "" ;
$ext = "";
$time = "";
}

if($type == 1)
$formatted_stamp = "$day/$month/$year".$time;
elseif($type==2)
{
$formatted_stamp = "$day/$month/$year";
}
elseif($type==3)
$formatted_stamp = $time;

return $formatted_stamp;
}
?>

PHP interview Question

1. How can we repair a MySQL table?
2. What are the advantages of stored procedures, triggers, indexes?
3. What is the maximum length of a table name, database name, and fieldname in MySQL?
4. How many values can the SET function of MySQL take?
5. What are the other commands to know the structure of table using MySQL commands except explain command?

PHP interview Preperation

1. What does a special set of tags 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?
$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 works, but 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 \023 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:



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.

The Difference Between require() and include()

The key difference between require() and include() is that if you require() a file that can't be loaded (eg if it isn't there) then it generates a fatal error which will halt the execution of the page completely, and no more output will be generated. On the other hand, if you include() a file that can't be loaded, then this will merely generate a warning and continue building the page.

What one you should use depends on the situation; require() is best suited for loading files that are essential to the rest of the page - for example if you have a database driven website then using require() to include a file containing the database login and password is clearly preferred over using include(). If you used include() in this situation, then you may end up generating more warnings and errors than you had intended.

include() should be used when it isn't essential for that file to be loaded to execute the page. This is best used in situations where the file isn't essential to the processing of the page (for example a footer file), so if the file isn't present then the user can still view the site. You should, of course, make sure that all files you include() and require() are going to be available.

In PHP versions prior to 4.0.2. there was slightly different behaviour of require(). If you used a require() statement in an if block then the require() statement will always make sure that the file you're require()ing is readable, regardless of whether the condition was true for that if block to be processed. This is best illustrated with the following code example:

$a = 1;
if($a == 2) {
require("header.php");
}
?>

In this example, PHP versions before 4.0.2. will always make sure that header.php is available, but it will only actually execute the contents of it if $a is equal to 2.

More Explanation:

The principle differences between include() & require() are :
(1).When “Include()”ed file is not found,only warnings will be displayed& the script will continue to execute further.
But,when “require()”ed file is not found,fatal errors will be displayed & the script will halt execution.
When we are dealing with non-confedintial data,
inlude()is preffered.
e.g. When we are dealing with a form which posts Sachin Tendulkar’s age & no. of centuries ,after posting the form,
the variables age & no.centuries will be displayed on the URL of the opened active file.
If “include()” ed file doesn’t exist ,only waning will be given & the script will follow its execution afterwatds.

with including “require()” in our file ,we can safely process over confidential data ,such as user login form. Here both login ID & passwords are checked & script will continue only when “require()” function gets required file,otherwise,it will halt the script showing fatal error.