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PHP卷曲字符串语法问题

php

4

zildjohn01 · 技术社区 · 16 年前

我在运行php 5.3.0。我发现只有当表达式的第一个字符是 $ . 是否有方法包括其他类型的表达式(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)}"

5 回复 | 直到 13 年前

1

2

Ignacio Vazquez-Abrams 16 年前

不可以。只有不同形式的变量才能用变量替换。

2

3

Davor Lucic 16 年前

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

3

2

Justin Gregoire 16 年前

看看这个链接 LINK

代码示例,

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.";
?>

有不同的事情,你可以实现与卷曲大括号,但它是有限的,取决于你如何使用它。

4

0

Timothy 16 年前

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

var_dump(new Foo());

5

0

Marc B 16 年前

通常,您不需要在变量周围加大括号,除非您需要强制PHP将某个对象视为变量,否则它的常规解析规则可能不需要。大的是多维数组。PHP的解析器不贪婪地决定什么是变量,什么不是变量,因此需要大括号来强制PHP查看数组元素的其余引用:

<?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