mehrere checkboxen zusammen abfragen

  $query2="INSERT INTO ResBar
      SET
        mo='$mo',
        di='$di',
	    mi='$mi',
	    do='$do',
	    fr='$fr',
	    sa='$sa',
	    so='$so', 

        <label for="montag">Mo.</label>
        <input name="mo" type="checkbox"  id="montag" value="montag">
        
        <label for="dienstag">Di.</label>
        <input name="di" type="checkbox"  id="dienstag" value="dienstag">
        
        <label for="mittwoch">Mi.</label>
        <input name="mi" type="checkbox"  id="mittwoch" value="mittwoch">
        
        <label for="donnerstag">Do.</label>
        <input name="do" type="checkbox"  id="donnerstag" value="donnerstag">
        
        <label for="freitag">Fr.</label>
        <input name="fr" type="checkbox"  id="freitag" value="freitag">
        
        <label for="samstag">Sa.</label>
        <input name="sa" type="checkbox"  id="samtag" value="samstag">
        
        <label for="sonntag">So.</label>
        <input name="so" type="checkbox"  id="sonntag" value="sonntag">

<script type="text/javascript">
function chkFormular ()

    if (document.Formular.di.value == "montag") {
    alert("Eingabe nicht möglich");
    document.Formular.di.focus();
    return false;
  }
</script>

<label for="montag">Mo.</label>
<input name="mo" type="checkbox"  id="montag" value="montag" onclick="chkFormular('mo')" />

<label for="dienstag">Di.</label>
<input name="di" type="checkbox"  id="dienstag" value="dienstag" onclick="chkFormular('di')" />

<label for="mittwoch">Mi.</label>
<input name="mi" type="checkbox"  id="mittwoch" value="mittwoch" onclick="chkFormular('mi')" />

<label for="donnerstag">Do.</label>
<input name="do" type="checkbox"  id="donnerstag" value="donnerstag" onclick="chkFormular('do')" />

<label for="freitag">Fr.</label>
<input name="fr" type="checkbox"  id="freitag" value="freitag" onclick="chkFormular('fr')" />

<label for="samstag">Sa.</label>
<input name="sa" type="checkbox"  id="samstag" value="samstag" onclick="chkFormular('sa')" />

<label for="sonntag">So.</label>
<input name="so" type="checkbox"  id="sonntag" value="sonntag" onclick="chkFormular('so')" />

<script type="text/javascript">
var check = 0;

function chkFormular (box) {

if (document.getElementById(box).checked == true) {
	check = check + 1;
} else if (document.getElementById(box).checked == false) {
	check = check - 1;
}

if (check == 7) {
	alert ("Es dürfen nicht alle Checkboxen markiert werden!");
	check = check - 1;
	document.getElementById(box).checked = false;
}

}
</script>