4. Strings Flashcards
When doing String interpolation, how can you assure that the correct variable is replaced?
Wrap the variable in ${var1}. Everything between curley braces will be evaluated.
How many times does String Interpolation run?
Only once, unlike variable variables in normal code.
What is a Heredoc? What’s the syntax?
<<< 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.
Does a Heredoc interpolate strings?
Yes
What’s the difference between printf() and sprintf()?
printf() – Writes directly to the screen.
sprintf() – Returns the built-up string so you can save it for future use.
What function is useful for debugging?
var_dump(), print_r() is as well but it doesn’t meaningfully display Bool or NULL so that’s why var_dump() is preferred.
How can you get the length of a string?
strlen() function.
What are the functions we can use to trim up whitespace in a string?
trim() – Left & right trimming.
ltrim() – Left trimming
rtrim() – Right trimming
How can we convert an entire string to uppercase or lowercase?
strtolower()
strtoupper()
Functions respectively.
What functions can we use to capitalize the first character of a string? What about the first letter of every word in a string?
ucfirst() – First character in the whole string
ucwords() – First character in all words.
How can you parse a string to a text representation of html?
htmlentities() function
How can you strip out html from a string?
strip_tags()
What function would you use for URL encoding? URL decoding?
rawurlencode()
rawurldecode()
How would you encode a query string? How about decoding?
urlencode()
urldecode()
How SHOULD you compare 2 strings? Why do you need to do it this way?
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.
How do you compare strings by natural order?
strncmp(str1, str2)
strncasecmp(str1, str2)
Give an example of natural order vs ASCII order? Think why we’d want to use natural order instead of just ASCII order.
What’s the function to get a substring?
substr($str, start, length)
if length is removed, it copies to the end of the string.
How can you count the number of times a substring occurs within a bigger string?
substr_count($big_string, $small_string)
How can you replace at a location in a string?
substr_replace($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 $original.
You can use negative values for the startIndex to start counting from the end of the string.
What function would you use to reverse a string?
strrev($string)
How do you Tokenize a string? What’s it useful for?
$firstChunk = strtok($string, $separator)
Then when you want the next chunk you just keep calling
$nextChunk = strtok($separator)
How do you use sscanf(), how is it useful?
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)
