If-Else with multiple condition PHP

for awhile i've been trying to make this code work for this form's database, but it just wouldn't work properly.

this is the form input without PI_ID this is the form input with PI_ID

$content = $_POST['cr_code'] . "-" . $_POST['cr_num'] . "-" . $_POST['cr_mon'] . "-" . $_POST['cr_year'] . "-" . $_POST['cr_modul'] . "-" . $_POST['cr_phase'] . "-" . $_POST['cr_pi_id'];

this output was faulty as the output will be "CR-001-08-18- -"if i dont want to input any module or phase, because of the lines behind 18 are not supposed to be there.

basically the output is CR-001-08-18-Marketing-PH1-PI1, the Module(Marketing),Phase(PH1),and PI_ID(PI1) is optional to fill so it could either be:

• CR-001-08-18-Marketing(Module filled, Phase unfilled, PI_ID unfilled)
• CR-001-08-18-PH1(Module unfilled, Phase filled, PI_ID Unfilled)
• CR-001-08-18-PI(Module unfilled, Phase unfilled, PI_ID filled)

this was the code i tried using if else

$phase=$_GET['cr_phase'];
$modul=$_GET['cr_modul'];
$crpid=$_GET['cr_pi_id'];

if ($phase!='' && $modul='' && $crpid='')
{
        $content = $_POST['cr_code'] . "-" . $_POST['cr_num'] . "-" . $_POST['cr_mon'] . "-" . $_POST['cr_year'] . "-" . $_POST['cr_phase'];
}else if($phase='' && $modul!='' && $crpid='')
{
        $content = $_POST['cr_code'] . "-" . $_POST['cr_num'] . "-" . $_POST['cr_mon'] . "-" . $_POST['cr_year'] . "-" . $_POST['cr_modul'];
}else if($phase='' && $modul='' && $crpid=!'')
{
        $content = $_POST['cr_code'] . "-" . $_POST['cr_num'] . "-" . $_POST['cr_mon'] . "-" . $_POST['cr_year'] . "-" . $_POST['cr_pi_id'];
}else if($phase!='' && $modul!='' && $crpid!='')
{
        $content = $_POST['cr_code'] . "-" . $_POST['cr_num'] . "-" . $_POST['cr_mon'] . "-" . $_POST['cr_year'] . "-" . $_POST['cr_modul'] . "-" . $_POST['cr_phase'] . "-" . $_POST['cr_pi_id'];
}else
{
        $content = $_POST['cr_code'] . "-" . $_POST['cr_num'] . "-" . $_POST['cr_mon'] . "-" . $_POST['cr_year'];
}

but it doesn't work as it just display "CR-001-08-18" without showing the phase and module, even when i inputted the phase, module, and PI_ID

anyone can help?