注: 一个字符串变得非常巨大也没有问题，PHP 没有给字符串的大小强加实现范围，所以完全没有理由担心长字符串。
注: 在 PHP 3 中，此情况下将发出一个 E_NOTICE 级的警告。
注: 和其他两种语法不同，单引号字符串中出现的变量和转义序列不会被变量的值替代。
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<?php echo 'this is a simple string'; echo 'You can also have embedded newlines in strings this way as it is okay to do'; // Outputs: Arnold once said: "I'll be back" echo 'Arnold once said: "I\'ll be back"'; // Outputs: You deleted C:\*.*? echo 'You deleted C:\\*.*?'; // Outputs: You deleted C:\*.*? echo 'You deleted C:\*.*?'; // Outputs: This will not expand: \n a newline echo 'This will not expand: \n a newline'; // Outputs: Variables do not $expand $either echo 'Variables do not $expand $either'; ?> |
| 序列 | 含义 |
|---|---|
| \n | 换行（LF 或 ASCII 字符 0x0A（10）） |
| \r | 回车（CR 或 ASCII 字符 0x0D（13）） |
| \t | 水平制表符（HT 或 ASCII 字符 0x09（9）） |
| \\ | 反斜线 |
| \$ | 美元符号 |
| \" | 双引号 |
| \[0-7]{1,3} | 此正则表达式序列匹配一个用八进制符号表示的字符 |
| \x[0-9A-Fa-f]{1,2} | 此正则表达式序列匹配一个用十六进制符号表示的字符 |
| 警告 | ||
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很重要的一点必须指出，结束标识符所在的行不能包含任何其它字符，可能除了一个分号（;）之外。这尤其意味着该标识符不能被缩进，而且在分号之前和之后都不能有任何空格或制表符。同样重要的是要意识到在结束标识符之前的第一个字符必须是你的操作系统中定义的换行符。例如在 Macintosh 系统中是 \r。 如果破坏了这条规则使得结束标识符不“干净”，则它不会被视为结束标识符，PHP 将继续寻找下去。如果在这种情况下找不到合适的结束标识符，将会导致一个在脚本最后一行出现的语法错误。 不能用定界符语法初始化类成员。用其它字符串语法替代。
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例子 11-4. 定界符字符串例子
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注: 定界符支持是 PHP 4 中加入的。
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<?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 ${beer}s"; // works echo "He drank some {$beer}s"; // works ?> |
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<?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."; ?> |
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<?php // Let's show all errors error_reporting(E_ALL); $great = 'fantastic'; // 不行，输出为：This is { fantastic} echo "This is { $great}"; // 可以，输出为：This is fantastic echo "This is {$great}"; echo "This is ${great}"; // Works echo "This square is {$square->width}00 centimeters broad."; // Works echo "This works: {$arr[4][3]}"; // This is wrong for the same reason as $foo[bar] is wrong // outside a string. In otherwords, it will still work but // because PHP first looks for a constant named foo, it will // throw an error of level E_NOTICE (undefined constant). echo "This is wrong: {$arr[foo][3]}"; // Works. When using multi-dimensional arrays, always use // braces around arrays when inside of strings echo "This works: {$arr['foo'][3]}"; // Works. echo "This works: " . $arr['foo'][3]; echo "You can even write {$obj->values[3]->name}"; echo "This is the value of the var named $name: {${$name}}"; ?> |
注: 为了向下兼容，仍然可以用方括号。不过此语法自 PHP 4 起已过时。
例子 11-5. 一些字符串例子
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<?php $foo = 1 + "10.5"; // $foo is float (11.5) $foo = 1 + "-1.3e3"; // $foo is float (-1299) $foo = 1 + "bob-1.3e3"; // $foo is integer (1) $foo = 1 + "bob3"; // $foo is integer (1) $foo = 1 + "10 Small Pigs"; // $foo is integer (11) $foo = 4 + "10.2 Little Piggies"; // $foo is float (14.2) $foo = "10.0 pigs " + 1; // $foo is float (11) $foo = "10.0 pigs " + 1.0; // $foo is float (11) ?> |
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<?php echo "\$foo==$foo; type is " . gettype ($foo) . "<br />\n"; ?> |
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