/**Script em Javascript para formatar o valor com virgula nas casas decimais no formulário**/
<script>
function FormataValor(id,tammax,teclapres) {
    
        if(window.event) { // Internet Explorer
         var tecla = teclapres.keyCode; }
        else if(teclapres.which) { // Nestcape / firefox
         var tecla = teclapres.which;
        }
    

vr = document.getElementById(id).value;
vr = vr.toString().replace( "/", "" );
vr = vr.toString().replace( "/", "" );
vr = vr.toString().replace( ",", "" );
vr = vr.toString().replace( ".", "" );
vr = vr.toString().replace( ".", "" );
vr = vr.toString().replace( ".", "" );
vr = vr.toString().replace( ".", "" );
tam = vr.length;

if (tam < tammax && tecla != 8){ tam = vr.length + 1; }

if (tecla == 8 ){ tam = tam - 1; }

if ( tecla == 8 || tecla >= 48 && tecla <= 57 || tecla >= 96 && tecla <= 105 ){
if ( tam <= 2 ){
document.getElementById(id).value = vr; }
if ( (tam > 2) && (tam <= 5) ){
document.getElementById(id).value = vr.substr( 0, tam - 2 ) + ',' + vr.substr( tam - 2, tam ); }
if ( (tam >= 6) && (tam <= 8) ){
document.getElementById(id).value = vr.substr( 0, tam - 5 ) + '.' + vr.substr( tam - 5, 3 ) + ',' + vr.substr( tam - 2, tam ); }
if ( (tam >= 9) && (tam <= 11) ){
document.getElementById(id).value = vr.substr( 0, tam - 8 ) + '.' + vr.substr( tam - 8, 3 ) + '.' + vr.substr( tam - 5, 3 ) + ',' + vr.substr( tam - 2, tam ); }
if ( (tam >= 12) && (tam <= 14) ){
document.getElementById(id).value = vr.substr( 0, tam - 11 ) + '.' + vr.substr( tam - 11, 3 ) + '.' + vr.substr( tam - 8, 3 ) + '.' + vr.substr( tam - 5, 3 ) + ',' + vr.substr( tam - 2, tam ); }
if ( (tam >= 15) && (tam <= 17) ){
document.getElementById(id).value = vr.substr( 0, tam - 14 ) + '.' + vr.substr( tam - 14, 3 ) + '.' + vr.substr( tam - 11, 3 ) + '.' + vr.substr( tam - 8, 3 ) + '.' + vr.substr( tam - 5, 3 ) + ',' + vr.substr( tam - 2, tam );}
}
}
</scirpt>
<form>
<input name="valor" type="text" id="valor" onKeyPress="FormataValor(this.id, 10, event)"     size="10" maxlength="10"  />
</form>

/**Script em PHP para formatar o valor para gravar no banco de dados usando a função str_replace**/
$valor = $_POST["valor"];
str_replace(",",".",str_replace(".","",$valor));

/**
- O primeiro str_replace [ que contem o $valor nao formatado ]
ira retirar os "." pontos
- o segundo str_replace ira trocar a "," por "."
**/

/**Agora para visualizar o valor do banco de dados utilizara o number_format**/
<?=number_format($campo['table_valor'], 2, ',','.')?>;