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PHP Interview Questions and Answers

Ques 21. I want to combine two variables together:

Ans.

 $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.

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Ques 22. For printing out strings, there are echo, print and printf. Explain the differences.
Ans. 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.
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Ques 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?
Ans. On large strings that need to be formatted according to some length specifications, use wordwrap() or chunk_split().
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Ques 24. What's the difference between htmlentities() and htmlspecialchars()?
Ans. htmlspecialchars only takes care of <, >, single quote ', double quote " and ampersand. htmlentities translates all occurrences of character sequences that have different meaning in HTML.
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Ques 25. What's the difference between md5(), crc32() and sha1() crypto on PHP?
Ans. 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.
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echo, print and printf. Explain the differences. 3) 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? 4) What's the difference between htmlentities() and htmlspecialchars()? 5) What's the difference between md5(), crc32() and sha1() crypto on PHP? " />

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