${ }（美元大括号）被称为复杂（卷曲）语法
：
之所以称其为“复杂”，是因为语法复杂，而是因为它允许使用复杂的表达式。
可以通过此语法包括具有字符串表示形式的任何标量变量，数组元素或对象属性。只需以与出现在字符串外部相同的方式编写表达式，然后将其包装在
{和中即可}。由于{无法转义，因此仅在$紧随其后的才会识别此语法{。使用{$得到文字{$。一些示例可以使您清楚：<?php// Show all errorserror_reporting(E_ALL);$great = 'fantastic';// Won't work, outputs: This is { fantastic}echo "This is { $great}";// Works, outputs: This is fantasticecho "This is {$great}";echo "This is ${great}";// Worksecho "This square is {$square->width}00 centimeters broad.";// Works, quoted keys only work using the curly brace syntaxecho "This works: {$arr['key']}";// Worksecho "This works: {$arr[4][3]}";// This is wrong for the same reason as $foo[bar] is wrong outside a// string. In other words, it will still work, but only because PHP// first looks for a constant named foo; an error of level E_NOTICE// (undefined constant) will be thrown.echo "This is wrong: {$arr[foo][3]}";// Works. When using multi-dimensional arrays, always use braces around// arrays when inside of stringsecho "This works: {$arr['foo'][3]}";// Works.echo "This works: " . $arr['foo'][3];echo "This works too: {$obj->values[3]->name}";echo "This is the value of the var named $name: {${$name}}";echo "This is the value of the var named by the return value of " . " getName(): {${getName()}}";echo "This is the value of the var named by the return value of " . "$object->getName(): {${$object->getName()}}";// Won't work, outputs: This is the return value of getName():{getName()}
echo “This is the return value of getName(): {getName()}”;
?>
