將常量（不可變）插入heredoc？

Question

<?php 
    define('my_const', 100); 
    echo <<<MYECHO 
     <p>The value of my_const is {my_const}.</p> 
MYECHO; 
?> 

如果我把大括號內的變量打印出來。但不是恆定的。我該怎麼做？ 謝謝！

Answer 1

使用sprintf()

define('my_const', 100); 
$string = <<< heredoc 
     <p>The value of my_const is %s.</p> 
heredoc; 

$string = sprintf($string, my_const); 

Answer 2

我知道，這已經已經回答了，但你也可以通過常量的值賦值給一個變量解決這個問題。

我個人是這麼做的，因爲如果你的字符串中有很多常量，那麼你的sprintf調用可能會非常混亂。這也很難掃描字符串，看看什麼在做什麼。另外，通過分別分配變量，您可以看到正在採取什麼值。

一個例子是：

$const = CONST; 
$variable = VARIABLE; 
$foo = (new Foo)->setFooProperty(12)->getFooProperty(); 
$bar = (123 - 456) * 10; 
$ten = 1 + 2 + 1 + (5 - 4); 
<<<EOD 
Lorem ipsum dolor sit amet, **$variable** adipiscing elit. 
Duis gravida aliquet dolor quis gravida. 
Nullam viverra urna a velit laoreet, et ultrices purus condimentum. 
Ut risus tortor, facilisis sed porta eget, semper a augue. 
Sed adipiscing erat non sapien commodo volutpat. 
Vestibulum nec lectus sed elit dictum accumsan vel adipiscing libero. 
**$const** vehicula molestie sapien. 
Ut fermentum quis risus ut pellentesque. 
Proin in dignissim erat, eget molestie lorem. Mauris pretium aliquam eleifend. 
**$foo** vitae sagittis dolor, quis sollicitudin leo. 
Etiam congue odio sit amet sodales aliquet. 
Etiam elementum auctor tellus, quis pharetra leo congue at. Maecenas sit amet ultricies neque. 
Nulla luctus enim libero, eget elementum tellus suscipit eu. 
Suspendisse tincidunt arcu at arcu molestie, a consequat velit elementum. 
Ut et libero purus. Sed et magna vel elit luctus rhoncus. 
Praesent dapibus consectetur tortor, vel **$bar** mauris ultrices id. 
Mauris pulvinar nulla vitae ligula iaculis ornare. 
Praesent posuere scelerisque ligula, id tincidunt metus sodales congue. 
Curabitur lectus urna, porta sed molestie ut, mollis vitae libero. 
Vivamus vulputate congue **$ten**. 
EOD; 

Answer 3

把你定義的變量爲簡單的變量和使用它包括在定界符就像在下面的例子：

<?php 
define('my_const', 100); 
$variable = my_const; 
    echo <<<MYECHO 
     <p>The value of my_const is {$variable}.</p> 
MYECHO; 
?> 

Answer 4

您還可以使用get_defined_constants功能。它把後面所有當前定義的常量數組中，您可以在您的定界符字符串中使用

// Let's say there is FOO and BAR defined 
$const = get_defined_constants(); 

$meta = <<< EOF 
    my awesome string with "{$const['FOO']}" and "{$const['BAR']}" constants 
EOF; 

Answer 5

這裏有一個小竅門，讓雙引號字符串和here文檔包含在大括號中的語法，包括常量任意表達式和其他函數調用。它使用一個函數名可以被分配給一個變量，然後稱爲定界符內的事實：

<?php 

// Declare a simple function 
function _placeholder($val) { return $val; } 
// and assign it to something short and sweet 
$_ = '_placeholder'; 

// or optionally for php version >= 5.3 
// Use a closure (anomynous function) like so: 
$_ = function ($val){return $val;}; 

// Our test values 
define('abc', 'def'); 
define('ghi', 3); 

$a=1; 
$b=2; 

function add($a, $b) { return $a+$b; } 

// Usage 
echo "b4 {$_(1+2)} after\n"; // outputs 'b4 3 after' 
echo "b4 {$_(abc)} after\n"; // outputs 'b4 def after' 
echo "b4 {$_(add($a, $b)+ghi*2)} after\n"; // outputs 'b4 9 after' 
$text = <<<MYEND 

Now the same in heredoc: 
b4 {$_(1+2)} after 
b4 {$_(abc)} after 
b4 {$_(add($a, $b)+ghi*2)} after 

MYEND; 
echo $text;