PHP卷积字符串语法问题

Question

我正在运行PHP 5.3.0。我发现，只有当表达式的第一个字符是$时，卷曲字符串语法才起作用。有没有办法包含其他类型的表达式（函数调用等）？

简单的例子：

<?php 
$x = '05'; 
echo "{$x}"; // works as expected 
echo "{intval($x)}"; // hoped for "5", got "{intval(05)}" 

Answer 1

号只有各种形式的变量可以使用可变的取代基取代。

Answer 2

看看这个链接的代码LINK

例，

Similarly, you can also have an array index or an object property parsed. With array indices, the closing square bracket (]) marks the end of the index. For object properties the same rules apply as to simple variables, though with object properties there doesn't exist a trick like the one with variables. 

<?php 
// These examples are specific to using arrays inside of strings. 
// When outside of a string, always quote your array string keys 
// and do not use {braces} when outside of strings either. 

// Let's show all errors 
error_reporting(E_ALL); 

$fruits = array('strawberry' => 'red', 'banana' => 'yellow'); 

// Works but note that this works differently outside string-quotes 
echo "A banana is $fruits[banana]."; 

// Works 
echo "A banana is {$fruits['banana']}."; 

// Works but PHP looks for a constant named banana first 
// as described below. 
echo "A banana is {$fruits[banana]}."; 

// Won't work, use braces. This results in a parse error. 
echo "A banana is $fruits['banana']."; 

// Works 
echo "A banana is " . $fruits['banana'] . "."; 

// Works 
echo "This square is $square->width meters broad."; 

// Won't work. For a solution, see the complex syntax. 
echo "This square is $square->width00 centimeters broad."; 
?> 

有不同的东西，你可以用大括号实现，但它是有限的，这取决于你如何使用它。

Answer 3

<?php 
$x = '05'; 
echo "{$x}"; 
$a = 'intval'; 
echo "{$a($x)}"; 
?> 

Answer 4

<?php 
class Foo 
{ 
    public function __construct() { 
     $this->{chr(8)} = "Hello World!"; 
    } 
} 

var_dump(new Foo()); 

Answer 5

一般来说，你不需要括号周围变量，除非你需要强制PHP对待的东西作为一个变量，在其正常的解析规则，否则可能不会。最大的是多维数组。 PHP的解析器对于决定什么是变量和什么不是，所以需要大括号来强制PHP查看剩余的数组元素引用：

<?php 

$arr = array(
    'a' => array(
     'b' => 'c' 
    ), 
); 

print("$arr[a][b]"); // outputs: Array[b] 
print("{$arr[a][b]}"); // outputs: (nothing), there's no constants 'a' or 'b' defined 
print("{$arr['a']['b']}"); // ouputs: c