PHP 提供了一些流程控制的替代语法，包括 if，while，for，foreach 和 switch。替代语法的基本形式是把左花括号（{）换成冒号（:），把右花括号（}）分别换成 endif;，endwhile;，endfor;，endforeach; 以及 endswitch;。
―――― PHP代码 ――――
if ($a == 5): ?>
A is equal to 5
endif; ?>
――――――――――――
在上面的例子中，HTML 内容“A is equal to 5”用替代语法嵌套在 if 语句中。该 HTML 的内容仅在 $a 等与 5 时显示。
替代语法同样可以用在 else 和 elseif 中。下面是一个包括 elseif 和 else 的 if 结构用替代语法格式写的例子：
―――― PHP代码 ――――
if ($a == 5):
print "a equals 5";
print "...";
elseif ($a == 6):
print "a equals 6";
print "!!!";
else:
print "a is neither 5 nor 6";
endif;
?>
――――――――――――
更多例子参见 while，for 和 if。
User Contributed Notes
流程控制的替代语法
ssttoo at hotmail dot com
06-Dec-2003 06:20
Nested ternary operators can be used, although not a "good programming practice", as it does not promote readability and is prone to errors.
―――― PHP代码 ――――
$one = true;
$two = true;
$result = ($one) ? "one" : (($two) ? "two" : "none"); // $result is "one"
$result = ($one) ? "one" : ($two) ? "two" : "none"; // $result is "two"
?>
――――――――――――
pemga at freemail dot hu
20-Nov-2003 06:11
My personal preference on alternating writing is like this:
$query="select * from books";
sizeof($myparam) and $query.=" where title like '%$myparam%'";
Which means: if (sizeof($myparam)) $query.= ...
You can even combine this with the ? structure.
Like:
$query="select * from books";
strlen($title) and $c1=" title like '%$title%'";
strlen($year) and $c2=" year=$year";
strlen($c1) and $q2=$c1;
strlen($c2) and $q2.= (strlen($q2)) ? "and $c2" : $c2;
strlen($q2) and $query.=" where $q2";
Well, how about this? Can it be done easier? :)
I think is is called lazy Vs eager calc.
StarLight pl.net.solutions@slt
06-Nov-2003 12:59
In response to justin at iqmail dot net note, the parse error is because of lazy coding and has nothing to do with mixing syntax ;-). You should put a semicolon at the end of the second multi-line if. This works and didn't bark (tested on php 4.0.3pl1):D
if (condition):
// code
if (another_condition) {
// multi-line code
}; //notice the semicolon
else:
?>
[html here]
endif;
?>
best regards,
StarLight
i a m 4 w e b w o r k at hotmail dot com
13-Oct-2003 04:38
Good tutorial on using alternative control structure syntax at:
paul at example dot com
06-Sep-2003 06:27
There is an other alternative syntax:
if ($a > 5) {
echo "big";
} else {
echo "small";
}
?>
can be replaced by:
echo $a > 5 ? "big" : "small";
?>
matheo at step dot polymtl dot ca
05-Sep-2003 04:37
You can use a short syntax for "if"
$a = (condition) ? value if condition is true : value if condition is false;
$a = 1 ;
$b = 2 ;
$is_a_bigger = ($a > $b) ? 1 : 0 ;
echo $a_is_bigger ;
# returns 0
$a = 2 ;
$b = 1 ;
$is_a_bigger = ($a > $b) ? 1 : 0 ;
echo $is_a_bigger ;
# returns 1
?>
christopher dot murtaghNO at mcgill dot SPAMca
16-May-2003 12:19
A comment to the above:
You shouldn't need to change your code syntax because of nested flow control statements. Instead you should strongly think about your coding style and getting a better text editor. For example, indent your structures and sub structures:
if($foo){
if($Bar){
}
else{
}
}
else{
for($i=0;$i<$foo;$i ){
}
}
Also, any text editor worth using for coding (emacs, vi(m), BBEdit, Elvis, etc..) should do bracket balancing in case you are really in deep.
frank at vista dot com
25-Jan-2002 03:26
The alternative syntax is useful for situations where other systems would use templates:
OCIDefineByName($stmt, 'NAME', &$name);
OCIDefineByName($stmt, 'SALARY', &$salary);
OCIExecute($stmt);
?>
justin at iqmail dot net
30-Dec-2000 04:03
This is also relevant when mixing styles and interspersing PHP with HTML. The following example gives a syntax error since it associates the else with the inner if.
if (condition):
// code
if (another_condition) {
// multi-line code
}
else:
?>
[html here]
endif;
?>
A way around this is to not mix syntax, and change the inner if to the alternate colon-based syntax.
技术文章
流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法流程控制的替代语法
阅读(227) | 评论(0) | 转发(0) |
