isset(_POST) not working properly

Question

I want to link this two file but not working, first file to mae option drop down form secon file to print image can any body give advise ?? Thank you for ur help

File option reg :

$spi1s[1]="01_SAT_MAX_DUR";
$spi1s[2]="01_SAT_MAX_INT";
$spi1s[3]="01_SAT_RTN_PRD";
$spi1s[4]="01_SAT_FREQ";
$spires1 = mysql_query("SELECT SPI FROM kekeringan where SPI like '%01_SAT%'");
$spirow1=mysql_fetch_array($spires1);
$spiTitle1=$spirow1["SPI"];
foreach ($spi1s as $spiTitle1) {
    echo "<option id=\"option\" value=\"".$spiTitle1."\" ";
    if (isset($_POST['plot']) && $_POST['plot'] == $spiTitle1) { echo "selected=\"SELECTED\" "; }
            echo ">
            $spiTitle1
    </option>";
    }
echo "<br />";
echo "<br />";echo "</select></td>\n";
echo "<input id='option' type=\"submit\" name=\"getringan\" value=\"Submit\" />\n";
echo "</form>\n";

File to print :

if(isset($_POST['getringan'])){
$spi1s[1]="01_SAT_MAX_DUR";
$spi1s[2]="01_SAT_MAX_INT";
$spi1s[3]="01_SAT_RTN_PRD";
$spi1s[4]="01_SAT_FREQ";
$spires1 = mysql_query("SELECT SPI FROM ringan where SPI like '%01_SAT%'");
$spirow1=mysql_fetch_array($spires1);
$spiTitle1=$spirow1["SPI"];

    $image = "<div id=\"plot_res\" style='border:    none;width:810px;height:610px;margin:auto;padding:auto;'>";

    if ($_POST['plot'] == "01_SAT_MAX") {
            $image .= "<center><img src=\"../data/4_0_0.png\" /></center>";
            $image .= "</div>";
            echo $image;
    } elseif ($_POST['plot'] == "SPI_01_SAT_MAX_INT"){
            $image .= "<center><img src=\"../data/4_1_0.png\" /></center>";
            $image .= "</div>";
            echo $image;
    } elseif ($_POST['plot'] == "SPI_01_SAT_RTN_PRD"){
            $image .= "<center><img src=\"../data/4_2_0.png\" /></center>";
            $image .= "</div>";
            echo $image;
    } elseif ($_POST['plot'] == "SPI_01_SAT_FREQ"){
            $image .= "<center><img src=\"../data/4_3_0.png\" /></center>";
            $image .= "</div>";
            echo $image;

    } else {echo "fail";}

Answer 1

try this

if (array_key_exists('getringan', $_POST)) {
    ...
}

or if it's could be also get

if (array_key_exists('getringan', $_REQUEST)) {
    ...
}