當用雙引號或者定界符指定字串時，其中的變數會被解析。
有兩種語法，一種簡單的和一種複雜的。簡單語法最通用和方便，它提供了解析變數，陣列值，或者物件屬性的方法。
複雜語法是 php 4 引進的，可以用花括號括起乙個表示式。
簡單語法
如果遇到美元符號（$），解析器會盡可能多地取得後面的字元以組成乙個合法的變數名。如果你想明示指定名字的結束，用花括號把變數名括起來。
<?php
$beer
= 'heineken'
;echo
"$beer's taste is great"
; // works, "'" is an invalid character for varnames
echo
"he drank some $beers"
;
// won't work, 's' is a valid character for varnames
echo
"he drank some $s"
; // works
echo
"he drank some s"
; // works
?>
同樣也可以解析陣列索引或者物件屬性。對於陣列索引，右方括號（]）標誌著索引的結束。物件屬性則和簡單變數適用同樣的規則，儘管對於物件屬性沒有像變數那樣的小技巧。
<?php
// these examples are specific to using arrays inside of strings.
// when outside of a string, always quote your array string keys
// and do not use when outside of strings either.
// let's show all errors
error_reporting
(e_all
);$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 ."
;// works but php looks for a constant named banana first
// as described below.
echo
"a banana is ."
;// 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 ***plex syntax.
echo
"this square is $square->width00 centimeters broad."
;?>
對於任何更複雜的情況，應該使用複雜語法。
複雜（花括號）語法
不是因為語法複雜而稱其為複雜，而是因為用此方法可以包含複雜的表示式。
事實上，用此語法你可以在字串中包含任何在名字空間的值。僅僅用和在字串之外同樣的方法寫乙個表示式，然後用 把它包含進來。因為不能轉義「
echo
"this is "
;// 可以，輸出為：this is fantastic
echo
"this is "
;echo
"this is $"
;// works
echo
"this square is 00 centimeters broad."
;// works
echo
"this works: "
;// this is wrong for the same reason as $foo[bar] is wrong
// outside a string. in otherwords, it will still work but
// because php first looks for a constant named foo, it will
// throw an error of level e_notice (undefined constant).
echo
"this is wrong: "
;// works. when using multi-dimensional arrays, always use
// braces around arrays when inside of strings
echo
"this works: "
;// works.
echo
"this works: "
. $arr
['foo'][3
];echo
"you can even write "
;echo
"this is the value of the var named $name: }"
;?>
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