Sharing of css and php notes involved in application development

Make some records about some problems encountered in the application and their solutions for future reference.
　1. Regarding the absolute positioning of layers.
There are two div layers, the main class div is the overall layer, and the cloud class div is the absolute positioning layer. The effect is to display a cloud gif image in the upper right corner of the screen. The div layout code is as follows:
Copy the code The code is as follows:

...

During the process, the cloud layer was placed in the main layer, causing IE to be unable to display the cloud layer. Finally, the problem was solved by placing the cloud layer outside the main layer and changing the main position to relative. The CSS code is as follows:
Copy code The code is as follows:
.main{
position:relative;
top:30px;
width:600px;
height:auto;
text-align:left;
background-color:#FFFFFF;
border:5px solid #FF0011;
}
.cloud {
background: url(../image/cloud.gif) no-repeat 100% 50%;
height: 171px;
position: absolute;
right: 0px;
top: 0px;
width: 345px;
z-index: 1000;
}

　　2. Implementation of drop-down box selection for year, month and day.
The drop-down box for year, month and day is very sluggish, and the date cannot change with the change of year and month. But this is a relatively basic solution, and I also refer to other people's methods on the Internet. We will look into newer methods later.
Copy the code The code is as follows:
$months = array (1 => 'January', 'February', 'March', 'April', 'May', 'June' , 'July', 'August', 'September', 'October', 'November', 'December');
$days = range(1,31);
$years = range(1930 ,2011);
echo '';
foreach ($years as $value) {
echo "$value year> ;";
if ($value == 1987) {
echo '1987';
}
}
echo '';
echo '';
foreach ($months as $key => $value) {
echo "$value" ;
}
echo '';
echo '';
foreach ($days as $value) {
echo " $value day";
}
echo '';
?>