Heredoc vs nowdoc php

In PHP, there are numerous ways to specify a string value. The two most frequent methods are using single or double quotations

Dấu ngoặc kép

With double quoted string, escape characters like \n, is regarded as a new line break and variables are replaced with their values. As in this example

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$hello = 'Hello';
echo " $hello\n World. ";

// output
// Hello
// World.

Dấu nháy đơn

When strings that are single quoted, they are treated as literal, meaning that escaped characters do not expand; for example, ‘\n’ will not create a new line. Variables are not replaced by the values assigned to them

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$hello = 'Hello';
echo '$hello\nWorld. ';

// output
// $hello\nWorld

When we wish to define a multiline string, things become messier. For example, on occasions, we need to include multi-line javascript in PHP such as

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function foo ( status , rowid )
{
    $ ("#reportsTo") . attr("size", 10);
}

Introducing Heredoc and Nowdoc

Luckily, PHP offers a better way to write multiple-line string variables directly with Heredoc and Nowdoc syntax

The basic rules for Heredoc and Nowdoc are

• * Starting with a “triple less-sign” before a unique identifier for the beginning and end of the string,
• * The delimiter must always be at the beginning of a line, without any spaces, letters, or other characters
• * The closing identifier must be on a new line, followed by a semi-colon, and with no white space before it

Ví dụ

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$size = 10;
echo <<
function foo(status, rowid)
{
    $("#reportsTo"). attr("size", $size);
}
EOT;

// Out put
// function foo(status, rowid)
// {
//  $("#reportsTo"). attr("size", 10);
// }

We could use any string to represent identifier to mark the start and end of the string. The triple less sign must always come before the opening identifier

Heredoc differs from Nowdoc in that it makes use of double-quoted strings. For escape sequences, etc. , parsing is performed inside a heredoc, but a nowdoc employs single-quoted texts and hence parsing is not performed

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$size = 10;
echo <<
function foo(status, rowid)
{
    $("#reportsTo"). attr("size", $size);
}
EOT;

// Output.
// function foo(status, rowid)
// {
//  $("#reportsTo"). attr("size", $size);
// }

Phần kết luận

Heredoc and nowdoc are handy alternatives to the more frequently used quoted string syntax in PHP for creating strings, especially string that spans multiple lines

So the next time when you dealing with a long string, try heredoc or nowdoc

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  What is Nowdoc in PHP?

  Nowdoc ¶ Nowdocs are to single-quoted strings what heredocs are to double-quoted strings. A nowdoc is specified similarly to a heredoc, but no parsing is done inside a nowdoc. The construct is ideal for embedding PHP code or other large blocks of text without the need for escaping.

  What is a heredoc PHP?

  Heredoc PHP syntax is a way to write large bloc of text inside PHP, without the classic single quote, double quotes delimiters . It relies on <<< and a token that will also mark the end of the string.

  Should I use heredoc?

  Heredoc's are a great alternative to quoted strings because of increased readability and maintainability . You don't have to escape quotes and (good) IDEs or text editors will use the proper syntax highlighting.

  What is need for heredoc in PHP?

  The heredoc syntax is a way to declare a string variable . The heredoc syntax takes at least three lines of your code and uses the special character <<< at the beginning.