<meta charset="utf-8">
<?php
    print "Wpisz identyikator studenta";
    print "<input type=text name=id_studenta><br>";
    print "<input type=submit name=ok value='szukaj studenta' disabled>";
    print "<form method=post action='zadanieDomowe1output.php'>";
    $c = pg_connect("host=sbazy user=s200805 dbname=s200805 password=01234");
$query="select id_studenta from studenci";
$r=pg_exec($c,$query);
$error=false;
$arr=[];
for($i=0;$i<pg_numrows($r);$i++){
    $x=pg_result($r,$i,0);
    array_push($arr,$x);
}

for($i=0;$i<count($arr);$i++){
    if($_GET['id_studenta']==$arr[$i]){
        echo '<script type="text/javascript">',
        'document.write("elo")',
        '</script>'
        ;
    }

}