Heredoc and Nowdoc Knowledge in PHP

Heredoc structure

HEREDOC syntactic structure:<<<. After the operator, you supply an identifier and then wrap the line. The string itself is followed by the end flag with the previously defined identifier.

<?php  
$content = <<<fdipzone  
 
The HEREDOC structure cannot be used to initialize the properties of a class. Since PHP 5.3, this limit is valid only for heredoc containing variables. The following example will make an error.
 
<?php  
class test{public  
      
$var = ' 123 ';  
      
Public $a = <<<fdipzone  
$var
fdipzone;  
      
}  
      
$obj = new test ();  
echo $obj->a;  
? >
 
In the HEREDOC structure, the variable is replaced, but the method does not. Be extra careful when you have complex variables.
 
<?php  
$var = ' 123 ';  
$content = <<<fdipzone  
$var time ();  
Fdipzone;  
      
Echo $content; 123 time ();  
? >
 
Nowdoc structure
 
NOWDOC syntactic structure is very much like heredoc structure, but Nowdoc does not perform parsing operation. This structure is ideal for embedding PHP code or other large pieces of text without escaping special characters.
 
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Nowdoc is the same as the HEREDOC structure tag <<<, but the following identifiers must be enclosed in single quotes, i.e. <<< ' EOF '. All rules of the HEREDOC structure apply equally to the NOWDOC structure, especially the rules for closing identifiers. Nowdoc only joined after the php5.3.
 
<?php  
$var = ' 123 ';  
$content = <<< ' Fdipzone '
$var time ();  
Fdipzone;  
      
Echo $content; $var time (); $var has not been replaced  
?>
 
The NOWDOC structure can be used in any static data environment, and the most typical example is the property or constant used to initialize the class. The following example will not go wrong, and you can compare the Heredoc example.
 
<?php  
class test{public  
      
$a = <<< ' Fdipzone '
$var
fdipzone;  
      
}  
      
$obj = new test ();  
echo $obj->a;  
? >