PHP expression <<<EOB

2018-05-29 13:38:20

I've been developing with PHP for some years now, and recently came across this code:

<?php
    echo <<<EOB
        <html>
        <head>
            <title>My title</title>
        </head>
        ...
    EOB;
?>

I've never seen this approach to print HTML, which seems to be pretty useful and less prone to some weird variable or double quote syntax error.

I've searched for some official information about this and only found a post of Rasmus talking about this.

What is a detailed explanation about this functionality and what does EOB mean? Maybe end of block?

This is known as heredoc syntax. The documentation will tell you everything you need to know.

Essentially, however:

A third way to delimit strings is the heredoc syntax: <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.

The closing identifier must begin in the first column of the line. Also, the identifier must follow the same naming rules as any other label in PHP: it must contain only alphanumeric characters and underscores, and must start with a non-digit character or underscore.

So EOB is just what the author chose as his delimiter, not really sure what it stands for in his case but the identifier can be whatever you want.

为了完整起见，PHP中的Heredoc继承自Perl，它本身是从Bourne shell继承而来的。

它叫做heredoc，在手册中有描述。

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