This article is intended for people who need to learn about PHP.
Read the manual:
All text must be written within either two single quotes or two double quotes, for example:
echo "This text is enclosed within two double quotes."; echo 'This text is enclosed within two single quotes (apostrophes).';
If you want to use an apostrophe as a part of your text and you're also using apostrophes to enclose the text, you must escape it. Escaping a character in PHP means putting a backslash in front of it.
echo 'If we hadn\'t escaped apostrophes in this text, we\'d get a parse error.';
If you use double quotes to mark some text, you would have to escape any of those in your text;
echo "This is a piece of text enclosed within \"double quotes\".";