if(isset($_POST['form_search']))
{
$search="SELECT * FROM lib_books INNER JOIN lib_categories ON (cat_id=bk_cat) WHERE 1 ";
if(isset($_POST['bk_isbn']) && $_POST['bk_isbn']!='')
{
$search.="and bk_isbn = '".$_POST['bk_isbn']."' ";
}
if(isset($_POST['bk_title']) && $_POST['bk_title']!='')
{
$search.="and bk_title like '%".$_POST['bk_title']."%' ";
}
if(isset($_POST['bk_author']) && $_POST['bk_author']!='')
{
$search.="and bk_author like '%".$_POST['bk_author']."%' ";
}
if(isset($_POST['bk_description']) && $_POST['bk_description']!='')
{
$search.="and bk_description like '%".$_POST['bk_description']."%' ";
}
if(isset($_POST['bk_cat']) && $_POST['bk_cat']!='')
{
$search.="and bk_cat = '".$_POST['bk_cat']."' ";
}
$search.="ORDER BY bk_cat, bk_title";
}
else
{
$search="SELECT * FROM lib_books INNER JOIN lib_categories ON (cat_id=bk_cat) ORDER BY bk_cat, bk_title";
}
<form action="" method="post" name="form1" id="form1">
<table align="center" cellpadding="3" dir="rtl">
<tr>
<th colspan="2" align="center" nowrap="nowrap" bgcolor="#BDDFE1">جستجو</th>
</tr>
<tr>
<td align="right">کد بین المللی:</td>
<td align="right"><input type="text" name="bk_isbn" value="" size="32" /></td>
</tr>
<tr>
<td align="right">عنوان:</td>
<td align="right"><input type="text" name="bk_title" value="" size="32" /></td>
</tr>
<tr>
<td align="right">مولف/مترجم:</td>
<td align="right"><input type="text" name="bk_author" value="" size="32" /></td>
</tr>
<tr>
<td align="right" valign="top">توضیحات:</td>
<td align="right"><textarea name="bk_description" cols="50" rows="5"></textarea></td>
</tr>
<tr>
<td colspan="2" align="center"><input name="submit" type="submit" value=" جستجو " /></td>
</tr>
</table>
<input name="form_search" type="hidden" id="form_search" value="form1" />
</form>
مشکلم اینه که نمی دونم cat_id=bk_cat این دوتا چی هستن ؟if(isset($_POST['form_search']))
{
$search="SELECT * FROM lib_books INNER JOIN lib_categories ON (cat_id=bk_cat) WHERE 1 ";
if(isset($_POST['bk_isbn']) && $_POST['bk_isbn']!='')
{
$search.="and bk_isbn = '".$_POST['bk_isbn']."' ";
}