Variable with an escaped value as an if statement - php

Question

I have the following if statement:
<?php
$title = esc_html( get_the_title() );
$sub_title = esc_html( get_field('sub_title') );
if ( get_field('sub_title') ) {
echo '<h1>'.$title.'</h1>';
echo '<h2>'.$sub_title.'</h2>';
}
else {
echo '<h1 class="nm">'.$title.'</h1>';
}
?>
Instead of this line:
<?php
if ( get_field('sub_title') ) {
echo '<h1>'.$title.'</h1>';
echo '<h2>'.$sub_title.'</h2>';
}
?>
I would like to use:
<?php
if ( $sub_title ) {
echo '<h1>'.$title.'</h1>';
echo '<h2>'.$sub_title.'</h2>';
}
?>
As the $sub_title variable has an escaped value, is it okay to use within an if statement?

Answer 1

As a manner of general principle, try to avoid using escaped data except at the point where you actually need the escapes. For instance, don't add HTML escaping until you get to the code that actually adds it to HTML. So I would write it as:
<?php
$title = esc_html( get_the_title() );
$sub_title = get_field('sub_title');
if ( $sub_title ) {
echo '<h1>'.$title.'</h1>';
echo '<h2>'.esc_html($sub_title).'</h2>';
}
else {
echo '<h1 class="nm">'.$title.'</h1>';
}
?>
In some cases, as in your code, it may not matter. Your if statement just cares whether the string is empty or not, and escaping an empty string doesn't add anything to it, so the result of the if will be the same.
But there are more complex cases where you might compare the string to another string, and depending on what you're comparing with it could change the result.
Similar advice applies when storing data in databases. Store the raw data, don't escape it then. Escape it after you retrieve it, when you're showing it on an HTML page. That way, when you perform queries that don't involve displaying the result in HTML (e.g. creating a CSV file, displaying in plain text, etc.), you don't have to contend with the escapes that might have been added.