How can I echo 'for' loop here - php

Question

I want to use $i into his PHP condition how can I do this? I have no idea how to echo into condition. plz see the code and if you can plz help me. thank you advanced.
<?php
for($i=1; $i<4; $i++) {
if($top_h_text_**I want to use $i here!**) {
?>
<li>
<?php
if($top_h_icon_**I want to use $i here!**) {
?>
<i class="<?php echo $top_h_icon_**I want to use $i here!**;?>"></i>
<?php
}
if($top_h_icon_**I want to use $i here!** == 'fa fa-envelope'){
?>
<span class="top_header_text"><?php echo $top_h_text_**I want to use $i here!**;?></span>
<?php
} else {
?>
<span class="top_header_text"><?php echo $top_h_text_**I want to use $i here!**;?></span>
<?php
}
?>
</li>
<?php
}
}
?>

Answer 1

To accomplish what you are trying to do, simply follow this example:
$top_h_text_**I want to use $i here!**
becomes
${"top_h_text_".$i}
So you basically take the string you want (which should be the name of an existing variable) and wrap it with ${}

Answer 2

If this is in fact WordPress, and your top_h_icon_ and top_h_text are in fact defined. This would be appropriate method for concatenation of your $i increment and the variables. This is how you join two parts to make a single string.
Note that with WordPress and outputting dynamic variables, you should escape them.
<?php
for ( $i = 1; $i < 4; $i++ ) {
if ( $top_h_text_ . $i ) {
?>
<li>
<?php
if ( $top_h_icon_ . $i ) {
?>
<i class="<?php echo esc_attr( $top_h_icon_ . $i ); ?>"></i>
<?php
}
if ( 'fa fa-envelope' === $top_h_icon_ . $i ) {
?>
<span class="top_header_text"><?php echo esc_attr( $top_h_text_ . $i ); ?></span>
<?php
} else {
?>
<span class="top_header_text"><?php echo esc_attr( $top_h_text_ . $i ); ?></span>
<?php
}
?>
</li>
<?php
}
}