php页面传值接接不到值解决方案

php页面传值接接不到值
当前页面为tp.php 有一个form表单要传值给当前页面，

当点击之后地址栏的确出现了传值内容 但是当前页面的语句却接不到值

请教各位高人帮忙看看是怎么回事

PHP code

<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->                       $sql = 'select * from phone';                    if(isset($_GET['yy'])){                echo "hjfkgljfdfffffffffffffff";//经测试 没有输出，即没有接到值                $screen=$_GET["screen"];                $moshi=$_GET["moshi"];                $system=$_GET["system"];                $xilie=$_GET["xilie"];                if ($moshi !='0'){                    if(strpos($sql,'where'))                        $sql.=' and `p_moshi`='.$moshi;                    else                        $sql.=' where `p_moshi`='.$moshi;                }                if ($screen!='0'){                    if(strpos($sql,'where'))                    $sql.=' and `p_screen`='.$screen;                    else                        $sql.=' where `p_screen`='.$screen;                }                if ($system!='0'){                    if(strpos($sql,'where'))                    $sql.=' and `p_system`='.$system;                    else                        $sql.=' where `p_system`='.$system;                }                if ($xilie!='0'){                    if(strpos($sql,'where'))                    $sql.=' and `p_xilie`='.$xilie;                    else                        $sql.=' where `p_xilie`='.$xilie;                }            }                                            echo $sql.'<br>';

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