$output="<p class="one"><small>".$newsletter_one. '</small></p>'
Generally, when we write short codes we publish HTML like the above one, and instead of echo use return function.
How should we write this one →
<span class="class2" id="class3-<?php echo $random;?>"> </span>
Like this →
$output="<span class="class2" id="class3-.$random."> </span>"
or does this has some flaws?
When you want to return a data combined with a string, you can use one of the following methods:
Either open and close the string using ':
return '<span class="class2" id="class3-' . $random . '"> </span>';
Or use the double quote:
return "<span class="class2" id='class3-{$random}'> </span>";
You can simply use $random without the {} curly brackets, but it’s easier to read if you use {}.
You can even use double quotes for the inner string, but you need to escape them:
return "<span class=\"class2\" id=\"class3-{$random}\"> </span>";
As pointed out in comments by @birgire, to make it more WordPressy, we can also escape the variable:
return sprintf( '<span class="class2" id="class3-%s"></span>', esc_attr( $random ) );