The difference between PHP Heredoc and Nowdoc and its characteristics

php heredoc and Nowdoc

Heredoc structure

HEREDOC syntactic structure:<<<. After the operator, provide an identifier, and then wrap the line. The next is the string itself, and finally the identifier defined earlier as the end flag.

<?php$content = <<<FDIPZONE
The HEREDOC structure cannot be used to initialize the properties of a class. Since PHP 5.3, this restriction is only valid for heredoc containing variables. The following example will cause an error.

<?phpclass test{public $var = ' 123 ';p ublic $a = <<<fdipzone$varfdipzone;} $obj = new test (); Echo $obj->a;? >
In the HEREDOC structure, the variable is replaced, but the method does not. Take extra care when you have complex variables.

<?php$var = ' 123 '; $content = <<<fdipzone$var time (); Fdipzone;echo $content; 123 time ();? >
Nowdoc structure

The syntactic structure of nowdoc is much like the heredoc structure, but the parsing operation is not performed in Nowdoc. This structure is ideal for embedding PHP code or other large pieces of text without escaping special characters.

Nowdoc the same tag <<< as the HEREDOC structure, but the following identifiers must be enclosed in single quotes , i.e. <<< ' EOF '. All the rules of the HEREDOC structure also apply to the NOWDOC structure, especially the rule that ends the identifier. Nowdoc was added after the php5.3.

<?php$var = ' 123 '; $content = <<< ' Fdipzone ' $var time (); Fdipzone;echo $content; $var time (); $var have not been replaced?>
The NOWDOC structure can be used in any static data environment, the most typical example being a property or constant used to initialize a class. The following example does not make an error and can be compared to the heredoc example.

<?phpclass test{public $a = <<< ' Fdipzone ' $varFDIPZONE;} $obj = new test (); Echo $obj->a;? >
This article explains the differences and features between PHP Heredoc and Nowdoc, and more about the PHP Chinese web.