PHP - string creation
Before you can use a string you have to create it! A string can be used directly in a function or it can be stored in a variable. Below we create the exact same string twice: first storing it into a variable and in the second case we send the string directly to echo.
$my_string = "Hello world!"; echo "Hello world!"; echo $my_string;
In the above example the first string will be stored into the variable $my_string, while the second string will be used in the echo and not be stored.
Remember to save your strings into variables if you plan on using them more than once! Below is the output from our example code. They look identical just as we thought.
PHP - string creation single quotes
Thus far we have created strings using double-quotes, but it is just as correct to create a string using single-quotes, otherwise known as apostrophes.
$my_string = 'Hello World!'; echo 'Hello World!'; echo $my_string;
If you want to use a single-quote within the string you have to escape the single-quote with a backslash \ . Like this: \' !
echo 'Hello - It\'s my world!';
PHP - string creation double-quotes
We have used double-quotes and will continue to use them as the primary method for forming strings. Double-quotes allow for many special escaped characters to be used that you cannot do with a single-quote string. Once again, a backslash is used to escape a character.
$newline = "A newline is \n"; $return = "A carriage return is \r"; $tab = "A tab is \t"; $dollar = "A dollar sign is \$"; $doublequote = "A double-quote is \"";
Note: If you try to escape a character that doesn't need to be, such as an apostrophe, then the backslash will show up when you output the string. These escaped characters are not very useful for outputting to a web page because HTML ignore extra white space. A tab, newline, and carriage return are all examples of extra (ignorable) white space. However, when writing to a file that may be read by human eyes these escaped characters are a valuable tool!
PHP - string creation heredoc
The two methods above are the traditional way to create strings in most programming languages. PHP introduces a more robust string creation tool called heredoc that lets the programmer create multi-line strings without using quotations. However, creating a string using heredoc is more difficult and can lead to problems if you do not properly code your string! Here's how to do it:
$my_string = <<<TEST breakinterview.com PHP Tutorials TEST; echo $my_string;
There are a few very important things to remember when using heredoc.
- Use <<< and some identifier that you choose to begin the heredoc. In this example we chose TEST as our identifier.
- Repeat the identifier followed by a semicolon to end the heredoc string creation. In this example that was TEST;
- The closing sequence TEST; must occur on a line by itself and cannot be indented!
Another thing to note is that when you output this multi-line string to a web page, it will not span multiple lines because we did not have any <br /> tags contained inside our string! Here is the output made from the code above.
Once again, take great care in following the heredoc creation guidelines to avoid any headaches.