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 PHP Questions

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Q:

Would you initialize your strings with single quotes or double quotes?

Answer 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.
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Q:

What is the difference between characters 23 and x23?

Answer The first one is octal 23, the second is hex 23
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Q:

Describe how to create a simple AD rotator script without using database in PHP.

Answer

Following are the steps to create a simple AD rotator script without using database in PHP:


- All the ad’s can be collected in one place and be displayed randomly.rand() function can be used for this purpose.


- In order to NOT use any database, a flat file can be used to store the ad’s.


- In order to store the Ad’s information (HTML code), a flat file say “ad.txt” can be created.


- The random number can be stored in a variable 


$result_random=rand(1, 100);


- Conditions can be checked to display the ad’s.


if($result_random<=70)


{


      echo "Display ad1";


}

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Q:

So if md5( ) generates the most secure hash, why would you ever use the less secure crc32( ) and sha1( )?

Answer 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.
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Q:

How can we get the browser properties using PHP?

Answer

By using
$_SERVER['HTTP_USER_AGENT']
variable.

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Q:

What’s the special meaning of __sleep and __wakeup?

Answer __sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.
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Q:

For printing out strings, there are echo, print and printf. Explain the differences.

Answer - 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.
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Q:

What does a special set of tags do in PHP?

Answer The output is displayed directly to the browser.
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