请教这个赋值句子哪里不对

请问这个赋值句子哪里不对？

$mailbody=<<


















  
		
    
Product NO. 
    
"$_POST['productnumber']"
  
  
		
    
Name
    
"$_POST['username']"
  
  
		
    
Promotion code 
    
"$_POST['promotion']"
  
  
		
    
Mobilephone
    
"$_POST['mobilephone']"
  
  
		
    
Age
    
"$_POST['age']"
  
  
		
    
Sex
    
"$_POST['sex']"
  
  
		
    
Address
    
}"$_POST['address']"
  
  
		
    
Prescription Type 
    
"$_POST['prescription']"
  
  
		
    
Single PD 
    
"$singlepd"
  
  
		
    
Right PD 
    
"$rightpd"
  
  
		
    
Left PD 
    
"$leftpd"
  
  
		
    
Right OD SPH 
    
"$_POST['odsph']"
  
  
		
    
Left OS SPH 
    
"$_POST['ossph']"
  
  
		
    
OD CYL 
    
"$_POST['odcyl']"
  
  
		
    
OS CYL 
    
"$_POST['oscyl']"
  
  
		
    
OD AXIS 
    
"$_POST['odaxis']"
  
  
		
    
OS AXIS 
    
"$_POST['oxaxis']"
  


mailbody;

echo mailbody;

------解决方案--------------------
把形如 "$_POST['productnumber']" 的改为 {$_POST['productnumber']} 这样