字串

單引號

指定一個簡單字串的最簡單的方法是用單引號（字元 '）括起來。

要表示一個單引號，需要用反斜線（\）轉義，和很多其它語言一樣。如果在單引號之前或字串結尾需要出現一個反斜線，需要用兩個反斜線表示。注意如果你試圖轉義任何其它字元，反斜線本身也會被顯示出來！所以通常不需要轉義反斜線本身。

echo 'this is a simple string';
echo 'You can also have embedded newlines in strings,
like this way.';
echo 'Arnold once said: "I\'ll be back"';
// output: ... "I'll be back"
echo 'Are you sure you want to delete C:\\*.*?';
// output: ... delete C:\*.*?
echo 'Are you sure you want to delete C:\*.*?';
// output: ... delete C:\*.*?
echo 'I am trying to include at this point: \n a newline';
// output: ... this point: \n a newline

雙引號

如果用雙引號（"）括起字串，PHP 懂得更多特殊字元的轉義序列：

此外，如果試圖轉義任何其它字元，反斜線本身也會被顯示出來！

雙引號字串最重要的一點是其中的變數名會被變數值替代。細節參見字串解析。

定界符

另一種給字串定界的方法使用定界符語法（“<<<”）。應該在 <<< 之後提供一個標籤，然後是字串，然後是同樣的標籤結束字串。

結束標籤必須從行的第一列開始。同樣，標籤也必須遵循 PHP 中其它任何標簽的命名規則：只能包含字母數字下劃線，而且必須以下劃線或非數字字元開始。

定界符文本表現的就和雙引號字串一樣，只是沒有雙引號。這意味著在定界符文本中不需要轉義引號，不過仍然可以用以上列出來的轉義代碼。變數會被展開，但當在定界符文本中表達複雜變數時和字串一樣同樣也要注意。

例子 7-2. 定界符字串例子 <?php $str = <<<EOD Example of string spanning multiple lines using heredoc syntax. EOD; /* More complex example, with variables. */ class foo { var $foo; var $bar; function foo() { $this->foo = 'Foo'; $this->bar = array('Bar1', 'Bar2', 'Bar3'); } } $foo = new foo(); $name = 'MyName'; echo <<<EOT My name is "$name". I am printing some $foo->foo. Now, I am printing some {$foo->bar[1]}. This should print a capital 'A': \x41 EOT; ?>

變數解析

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，或者對象屬性的方法。

複雜語法是 PHP 4 引進的，可以用大括號括起一個表達式。

$beer = 'Heineken';
echo "$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 ${beer}s"; // works

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

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

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.";

$great = 'fantastic';
echo "This is { $great}"; // 不行，輸出為：This is { fantastic}
echo "This is {$great}";  // 可以，輸出為：This is fantastic
echo "This square is {$square->width}00 centimeters broad."; 
echo "This works: {$arr[4][3]}";     

// This is wrong for the same reason
// as $foo[bar] is wrong outside a string. 
echo "This is wrong: {$arr[foo][3]}"; 

echo "You should do it this way: {$arr['foo'][3]}";
echo "You can even write {$obj->values[3]->name}";
echo "This is the value of the var named $name: {${$name}}";

連接字串中的字元

字串中的字元可以通過在字串之後用大括號指定所要字元從零開始的偏移量來連接。

例子 7-3. 一些字串例子 <?php /* Assigning a string. */ $str = "This is a string"; /* Appending to it. */ $str = $str . " with some more text"; /* Another way to append, includes an escaped newline. */ $str .= " and a newline at the end.\n"; /* This string will end up being '<p>Number: 9</p>' */ $num = 9; $str = "<p>Number: $num</p>"; /* This one will be '<p>Number: $num</p>' */ $num = 9; $str = '<p>Number: $num</p>'; /* Get the first character of a string */ $str = 'This is a test.'; $first = $str{0}; /* Get the last character of a string. */ $str = 'This is still a test.'; $last = $str{strlen($str)-1}; ?>