Can I echo a variable with single quotes?

No. Variables (and special characters) only expand in strings delimited with double quotes. If you want to include a variable in a single-quote delimited string, you have to concatenate it instead:

echo 'I love my '.$variable.'.';

You could also escape the double quotes of your HTML if you'd rather use strings delimited by doble quotes:

echo "<a href=\"$url\">$text</a>";

See the PHP manual on strings, especially the part on string parsing, for more information.

No. ' will not parse variables. use

echo 'I love my '.$variable.'.';

or

echo "I love my {$variable}. And I have \" some characters escaped";