PHP Decode

<?php //php code that does the physics calculating of the inputted values and outputs the correct value 
	$A=$_POST ["a"]; $B=$_POST ["b"]; $C=$_POST ["c"]; $D=$_POST ["d"]; $E=$_POST ["e"]; $H=$_POST ["h"]; //grabs the different values of the different numbers and makes them variables 
	$t1=$_POST ["t1"]; $t2=$_POST ["t2"]; $t3=$_POST ["t3"]; $t4=$_POST ["t4"]; $t5=$_POST ["t5"]; $t6=$_POST ["t6"]; //grabs the different values for the checkboxs and makes them variables 
	if ($t1=isset and $t4=isset and $t6=isset) {$F=$B*M_PI*($D^2)*$C;} elseif ($t2=isset and $t7=isset and $t5=isset or $t2=isset and $t7=isset and $t6=isset) {$F=$H*M_PI*($E^2)*$C} else {$F=$A;} //the rest of this is the code that takes the newly created variable and caluclates them 
	$I=abs($F/(2*M_PI*$E*$A*(8.85*(10^(-12))))); 
	$J=(($A*($E^2))/($D^2)); 
	if ($t1=isset and $t3=isset and $t5=isset or $t1=isset and $t4=isset and $t5=isset) {echo "The answer to everything is 0 because of Gausse's Law";} 
	if ($t1=isset and $t3=isset and $t6=isset) {echo "The net charge is " . $F; echo "The electric field is " . $I;} 
	if ($t1=isset and $t4=isset and $t6=isset) {echo "The net charge is " . $F; echo "The electric field is " . $I;} 
	if ($t2=isset and $t3=isset and $t5=isset) {echo "The net charge is " . $J; echo "The electric field is " . $I;} 
	if ($t2=isset and $t3=isset and $t6=isset) {echo "The net charge is " . $F; echo "The electric field is " . $I;} 
	if ($t2=isset and $t7=isset and $t5=isset) {echo "The net charge is " . $F; echo "The electric field is " . $I;} 
	if ($t2=isset and $t7=isset and $t6=isset) {echo "The net charge is " . $F; echo "The electric field is " . $I;} 
?>