How to echo echo $ arrayReturn and html code [duplicate]

Remove the <? ?> delimiters, enclose the code in double quotation marks, and concatenate:

<?php
echo "<li>Número: 
    <strong>".$arrayReturn['numero']."</strong>
</li>";
?>

To give echo in an array you can use the function print_r()

<strong> <?php print_r($arrayReturn);?> </strong>

Sorry to leave the preformatted code on the screen you can do

<pre>
    <strong> <?php print_r($arrayReturn);?> </strong>
</pre>