Just use some template engine.
The most familiar one is PHP itself.
here is the very basic example of CRUD application:
the logic part doing only data manipulation
<?
mysql_connect();
mysql_select_db("new");
$table = "test";
if($_SERVER['REQUEST_METHOD']=='POST') { //form handler part:
$name = mysql_real_escape_string($_POST['name']);
if ($id = intval($_POST['id'])) {
$query="UPDATE $table SET name='$name' WHERE id=$id";
} else {
$query="INSERT INTO $table SET name='$name'";
}
mysql_query($query) or trigger_error(mysql_error()." in ".$query);
header("Location: http://".$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF']);
exit;
}
if (!isset($_GET['id'])) { //listing part:
$LIST=array();
$query="SELECT * FROM $table";
$res=mysql_query($query);
while($row=mysql_fetch_assoc($res)) $LIST[]=$row;
include 'list.php';
} else { // form displaying part:
if ($id=intval($_GET['id'])) {
$query="SELECT * FROM $table WHERE id=$id";
$res=mysql_query($query);
$row=mysql_fetch_assoc($res);
foreach ($row as $k => $v) $row[$k]=htmlspecialchars($v);
} else {
$row['name']='';
$row['id']=0;
}
include 'form.php';
}
?>
and two simple templates responsible for output,
form.php
<? include TPL_TOP ?>
<form method="POST">
<input type="text" name="name" value="<?=$row['name']?>"><br>
<input type="hidden" name="id" value="<?=$row['id']?>">
<input type="submit"><br>
<a href="?">Return to the list</a>
</form>
<? include TPL_BOTTOM ?>
and list.php
<? include TPL_TOP ?>
<a href="?id=0">Add item</a>
<? foreach ($LIST as $row): ?>
<li><a href="?id=<?=$row['id']?>"><?=$row['name']?></a>
<? endforeach ?>
<? include TPL_BOTTOM ?>
Though there are plenty of other template engines, of different kinds and ideologies.