4. Strings

Question 1

When doing String interpolation, how can you assure that the correct variable is replaced?

Answer 1

Wrap the variable in ${var1}. Everything between curley braces will be evaluated.

Question 2

How many times does String Interpolation run?

Answer 2

Only once, unlike variable variables in normal code.

Question 3

What is a Heredoc? What’s the syntax?

Answer 3

<<< Identifier

You choose an identifier, whatever you want. Then next line start writing your string and end with your identifier by itself with a semi-colon.

Question 4

Does a Heredoc interpolate strings?

Answer 4

Yes

Question 5

What’s the difference between printf() and sprintf()?

Answer 5

printf() – Writes directly to the screen.

sprintf() – Returns the built-up string so you can save it for future use.

Question 6

What function is useful for debugging?

Answer 6

var_dump(), print_r() is as well but it doesn’t meaningfully display Bool or NULL so that’s why var_dump() is preferred.

Question 7

How can you get the length of a string?

Answer 7

strlen() function.

Question 8

What are the functions we can use to trim up whitespace in a string?

Answer 8

trim() – Left & right trimming.

ltrim() – Left trimming

rtrim() – Right trimming

Question 9

How can we convert an entire string to uppercase or lowercase?

Answer 9

strtolower()

strtoupper()

Functions respectively.

Question 10

What functions can we use to capitalize the first character of a string? What about the first letter of every word in a string?

Answer 10

ucfirst() – First character in the whole string

ucwords() – First character in all words.

Question 11

How can you parse a string to a text representation of html?

Answer 11

htmlentities() function

Question 12

How can you strip out html from a string?

Answer 12

strip_tags()

Question 13

What function would you use for URL encoding? URL decoding?

Answer 13

rawurlencode()

rawurldecode()

Question 14

How would you encode a query string? How about decoding?

Answer 14

urlencode()

urldecode()

Question 15

How SHOULD you compare 2 strings? Why do you need to do it this way?

Answer 15

strcmp(str1, str2)

OR strcasecmp(str1, str2) which converts to lower before comparing.

They return a number less than 0 of str1 sorts before str2, and a number greater than 0 if str2 sorts before str1.

We need to use these functions because if you accidentally compared a string to an integer, it will cast the string to an int and try to do a comparison that we didn’t intend to do.

Question 16

How do you compare strings by natural order?

Answer 16

strncmp(str1, str2)

strncasecmp(str1, str2)

Question 17

Give an example of natural order vs ASCII order? Think why we’d want to use natural order instead of just ASCII order.

Answer 17

Question 18

What’s the function to get a substring?

Answer 18

substr($str, start, length)

if length is removed, it copies to the end of the string.

Question 19

How can you count the number of times a substring occurs within a bigger string?

Answer 19

substr_count($big_string, $small_string)

Question 20

How can you replace at a location in a string?

Answer 20

substr_replace($original, $new_replace, startIndex, length)

If you put a length of 0, it will insert without deleting.

If you use an empty string for $new_replace, it will simply remove from the $original.

You can use negative values for the startIndex to start counting from the end of the string.

Question 21

What function would you use to reverse a string?

Answer 21

strrev($string)

Question 22

How do you Tokenize a string? What’s it useful for?

Answer 22

$firstChunk = strtok($string, $separator)

Then when you want the next chunk you just keep calling

$nextChunk = strtok($separator)

Question 23

How do you use sscanf(), how is it useful?

Answer 23

We can get an array of fields (similar to a printf formatting)

$array = sscanf($string, $template)

OR we can provide the variables that will be where results are stored

$count = sscanf($string, $template, $var1 … $var9)