You really need to read string functionality
Every string literal must be delimted by the same thing on both sides of the string literal. Excluding heredoc and nowdoc syntax, that means either having " both before and after the string literal, or having ' both before and after the string literal. PHP interpretation of the string literal will differ depending on which delimiter you use and what the string contains.
$string = "it is a string";
$string = 'it is a string';
$string = "it's a string";
$string = 'it"s a string'; # works, but " shouldn't be used instead of ' in the english language
# this also works, because we now I escape the first ' (otherwise the string would end
# before the first ', i.e. after "it")
$string = 'it\'s a string';
$string = 'it\'s a "string"';
$string = "it's a \"string\"";
Also, use an editor with syntax highlighting (colorization of code) and it's suddenly very easy to see where string literals begin and end. This forum has syntax highlighting for php code found within php tags, for example
echo "String's are not always properly "escaped" but it's easy to see this (the blue text)";
