Procurar utilizando combobox*

<?php

if ($_POST['a'] == 'tudo'){
$sql = ("select * from ciffras order by nome asc" );

} else if ($_POST['abecedario'] == 'a'){
 $sql = ("select * from ciffras order by nome asc LIKE 'a%'");
} else if ($_POST['abecedario'] == 'b'){
 $sql = ("select * from ciffras order by nome asc LIKE 'b%'");
} else if ($_POST['abecedario'] == 'c'){
 $sql = ("select * from ciffras order by nome asc LIKE 'c%'");
} else if ($_POST['abecedario'] == 'd'){
 $sql = ("select * from ciffras order by nome asc LIKE 'd%'");
}

?>

<form action="index.php?pagina=ciffrasuti" method="post">

<label id="textonormal">Procurar por :</label>

 <select name="abecedario">
<option value="tudo">Tudo</option>
<option value="a">A</option>
<option value="b">B</option>
<option value="c">C</option>
<option value="d">D</option>
<option value="e">E</option>
<option value="f">F</option>
<option value="g">G</option>
<option value="h">H</option>
<option value="i">I</option>
<option value="j">J</option>
<option value="k">K</option>
<option value="l">L</option>
<option value="m">M</option>
<option value="n">N</option>
<option value="o">O</option>
<option value="p">P</option>
<option value="q">Q</option>
<option value="r">R</option>
<option value="s">S</option>
<option value="t">T</option>
<option value="u">U</option>
<option value="v">V</option>
<option value="w">W</option>
<option value="x">X</option>
<option value="y">Y</option>
<option value="z">Z</option>
 </select>

<input type="submit" name="button" class="classname" value="OK"/> <br /><br />