Use PHP's $_POST or $_GET superglobals to retrieve the value of the input tag via the name of the HTML tag
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<form method="post">
<input type="text" name="deleteinput" class="button"/>
<input type="submit" name="deletebtn" class="button" value="Delete single user data"/>
</form>
// php
<?php
$name = $_POST['deleteinput'];
echo $name;
?>