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Heredoc and Nowdoc in Category: PHP by amit
🕙 Posted on 2023-05-12 at 06:34:06 Read in Hindi ...
Heredoc & Nowdoc
Heredoc and Nowdoc are two newer ways to handle string data-type, as they are placed in a pair of double quotes or a pair of single quotes, respectively. ` (tick symbol, just left to 1 key in the keyboard) is used in pair, in ECMAScript 2015 or ES6 (in JavaScript) in the same way as Heredoc works in PHP. You can use any special characters inside Heredoc and Nowdoc without help of escape sequences. Backslash is also treated as literal in these two ways.
Heredoc and Nowdoc, both are written with an unique identifier at the beginning and at the end of the string. The beginning identifier in both HEREDOC and NOWDOC, are prefixed with <<< (three less than symbol), written without any space between them and also, without any space with the identifier. You must use some random UNIQUE text, which will not be used as identifier within the string! If any text inside the string is found same as opening IDENTIFIER, then that text will close the string, and you will get ERROR. You must add ; (semi-colon symbol) after the ending or closing identifier.
HEREDOC treats string as enclosed in a pair of double quotes
Beginning identifier either enclosed within a pair of double quotes, or without double quotes or without single quotes, make it HEREDOC. You have to make proper indentation when using HEREDOC & NOWDOC. The VSCode Editor and other modern code editors will show ERROR (underlined in red color squigly line), when there is no proper indentation, and it will also be shown in web-browser.
Parse error: Invalid body indentation level (expecting an indentation level of at least 2) in C:\xampp\htdocs\php_project\phptest.php on line 4
Any space with spacebar key or Tab key, or line-break with Enter/Return key shall be counted in both HEREDOC and NOWDOC. Do not place comments inside HEREDOC or NOWDOC, because these will be treated as STRING data-type, and PHP will not process them as comment. nl2br() is a pre-defined (built-in) PHP function, (generally used,) to insert the <br> HTML element, where the line-feed is inserted either with \n or Enter/
<?php
$one = 'abcd'; $two = 'efgh'; $three = 'ijkl'; $four = 'mnop';
$text = <<<IDENTIFIER
line $one
line $two
line $three
line $four
IDENTIFIER;
echo nl2br( $text );?><br />
line efgh
line ijkl
line mnop
<?php
$one = 'abcd'; $two = 'efgh'; $three = 'ijkl'; $four = 'mnop';
$text = <<<"TEXTIDENTIFIER"
line$one
line$two
line$three
line$four
TEXTIDENTIFIER;
echo nl2br( $text );?><br />
lineefgh
lineijkl
linemnop
Nowdoc treats string as enclosed in a pair of single quotes
Beginning identifier enclosed in a pair of single quotes makes it NOWDOC. Variables are not expanded to their values, in following example:
<?php
$one = 'abcd'; $two = 'efgh'; $three = 'ijkl'; $four = 'mnop';
$text = <<<'NEWIDENTIFIER'
line $one
line $two
line $three
line $four
NEWIDENTIFIER;
echo nl2br( $text );?><br />
line $two
line $three
line $four
Heredoc & Nowdoc are generally used to insert HTML structure
<?php
$html_structure = <<<UNIQUETEXT<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>R.I.B.H.U. Academy</title>
<style type="text/css">
/* === EMBEDDED CSS STYLES === */
.example { background-color: skyblue; font-size: 2rem; width: 50%; }
</style>
</head>
<body>
<div class="example">
<p> WELCOME TO RIBHU ACADEMY </p>
<div>
<script type="text/javascript">
// JavaScript codes ...
</script>
</body>
</html>
UNIQUETEXT;?>
<?php echo $html_structure; ?>
<?php var_dump( $html_structure ); ?>
Caution: Though var_dump() function can display the output in the web-browser, but you should avoid using it, when the string contains any HTML Doctype declaration.
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>R.I.B.H.U. Academy</title>
<style type="text/css">
/* === EMBEDDED CSS STYLES === */
.example { background-color: skyblue; font-size: 2rem; width: 50%; }
</style>
</head>
<body>
<div class="example">
<p> WELCOME TO RIBHU ACADEMY </p>
<div>
<script type="text/javascript">
// JavaScript codes ...
</script>
</body>
</html>"
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Amit Sinha March 2nd, 2023 at 9:30 PM
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Ribhu March 3rd, 2023 at 9:30 PM
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