I'll leave you an example that I hope will guide you:
first you need to have a form where to show your options of query or filter in your case is a select:
<form action="consultar.php" method="POST">
<select name="filtro" id="filtro" required>
<option selected disabled>Seleccione:</option>
<option value="1">Id</option>
<option value="2">Telefono</option>
</select>
<input type="text" name="variable" id="variable" required>
<input type="submit" value="Consultar">
</form>
File that receives your filter or search parameter ( query.php ):
<?php
$filtro = $_POST['filtro'];
$variable = $_POST['variable'];
if($filtro == 1){
$query =" SELECT * FROM gente WHERE id LIKE $variable ";
}
if($filtro == 2){
$query =" SELECT * FROM gente WHERE telefono LIKE $variable ";
}
...
...
..
?>
what is done in the file is to receive the parameter sent by your form, then using an if in this case valid filter or parameter and as armo or create the statement sql ($ query) ...
I hope I will guide you .. !!