- print_r: documentation ( source)
- array_diff: documentation ( source)
<?php
$selected=array('11a_Ma1','11a_Sc2','11b_Ls1');
$already=array('11SJP','11a_Ma1','11a_Sc2');
print_r(array_diff($selected,$already));
print_r(array_diff($already,$selected));
$a1=array(1,2,3);
$a2=array(1,2,3);
$ad=array_diff($a1,$a2);
if(isset($ad)){echo "YEAH";}
if(!empty($ad)){echo "YEAH";}