第三章 php操作符與控制結(jié)構(gòu)代碼
Jun 13, 2016 pm 12:03 PM
一．字符串插入
雙引號與單引號的區(qū)別：
1.雙引號的使用：
復制代碼 代碼如下:
//雙引號可以解析變量和轉(zhuǎn)義字符
$username = "jack";
echo "his name is $username!";
echo "
";
$username = "小東";
//如果是英文的感嘆號會正常解析變量
echo "他的名字是$username!";//他的名字是小東!
echo "
";
//如果是中文的感嘆號則會解析不出來
echo "他的名字是$username！";//他的名字是
echo "
";
//轉(zhuǎn)義字符在這里雖然被解析出來了，但是\n是在源代碼里換行
//瀏覽器顯示只是一個字符的位置
echo "他的名字是$username,\n他今年20歲了";//他的名字是小東, 他今年20歲了
echo "
";
//為了避免出現(xiàn)錯誤，推薦使用字符串連接的方式
echo "他的名字是".$username.",他今年20歲了";//他的名字是小東,他今年20歲了
?>
2.單引號的使用：
復制代碼 代碼如下:
//單引號只是輸出字符串字面值，
//不會解析變量和轉(zhuǎn)義字符。
//也不會進行語法加亮提示
$username = 'anllin';
echo 'his name is $username,\n his age is 20.';
//output
//his name is $username,\n his age is 20.
?>
部分常用的轉(zhuǎn)義字符
|
轉(zhuǎn)義序列 |
描述 |
|
\n |
換行符 |
|
\r |
回車 |
|
\t |
水平制表圖 |
|
\\ |
反斜杠 |
|
\$ |
美元符 |
|
\” |
雙引號 |
二．操作符
復制代碼 代碼如下:
//算術(shù)操作符
$a = 5;
$b = 3;
echo $a + $b;
echo '
';
echo $a - $b;
echo '
';
echo $a * $b;
echo '
';
echo $a / $b;
echo '
';
echo $a % $b;
?>
8
2
15
1.66666666667
2
復制代碼 代碼如下:
//復合賦值操作符
$a = 5;
$b = 3;
echo $a += $b;
echo '
';
echo $a -= $b;
echo '
';
echo $a *= $b;
echo '
';
echo $a /= $b;
echo '
';
echo $a %= $b;
echo '
';
echo $a .= $b;
?>
8
5
15
5
2
23
復制代碼 代碼如下:
//遞增遞減運算符
$a = 5;
echo ++$a;
echo '
';
echo $a++;
echo '
';
echo --$a;
echo '
';
echo $a--;
?>
6
6
6
6
復制代碼 代碼如下:
$a = 5;
$b = 3;
$c = 5;
$d = '5';
echo $a == $c;
echo '
';
echo $a === $c;
echo '
';
echo $a == $d;
echo '
';
echo $a != $b;
echo '
';
echo $a !== $d;
echo '
';
echo $a != $b;
echo '
';
echo $a > $b;
echo '
';
echo $b echo '
';
echo $a >= $c;
echo '
';
echo $a ?>
1
1
1
1
1
1
1
1
1
1
復制代碼 代碼如下:
$a = false;
echo ! $a;
echo '
';
$b = 5;
$c = 3;
echo $b > 0 && $c > 0;
echo '
';
echo $b > 0 and $c > 0;
echo '
';
echo $b != 0 || $c != 0;
echo '
';
echo $b != 0 or $c != 0;
echo '
';
?>
1
1
1
1
1
運算符”and”和”or”比&&和||的優(yōu)先級要低
三元操作符
復制代碼 代碼如下:
$a = 100;
echo $a > 60 ? 'success':'fail';
?>
success
錯誤抑制操作符
復制代碼 代碼如下:
echo @(100/0);
?>
?
?
三．控制結(jié)構(gòu)If條件判斷語句
復制代碼 代碼如下:
$a = 10;
if ($a > 0)
{
echo '整數(shù)大于零';
}
echo '
';
if ($a > 0)
{
echo '整數(shù)大于零';
}
else if($a {
echo '整數(shù)小于零';
}
else
{
echo '整數(shù)等于零';
}
?>
Switch語句
復制代碼 代碼如下:
$role = 'admin';
switch ($role)
{
case 'admin' :
echo '管理員';
break;
case 'user' :
echo '普通用戶';
break;
case 'guest' :
echo '游客';
break;
default :
echo '游客';
break;
}
?>
While循環(huán)語句
復制代碼 代碼如下:
$a = 10;
while ( $a > 0 )
{
echo $a --;
echo '
';
}
?>
Do while 循環(huán)語句
復制代碼 代碼如下:
$a = 10;
do
{
echo $a --;
echo '
';
}
while ( $a > 0 )
?>
For循環(huán)語句
復制代碼 代碼如下:
for($a = 0; $a {
echo $a;
echo '
';
}
?>
Break語句
復制代碼 代碼如下:
for($a = 0; $a {
echo $a;
echo '
';
if($a ==5)
{
break;//終止循環(huán)，但執(zhí)行循環(huán)后面的語句
}
}
echo '循環(huán)結(jié)束';
?>
Exit語句
復制代碼 代碼如下:
for($a = 0; $a {
echo $a;
echo '
';
if($a ==5)
{
exit;//直接退出，循環(huán)后面的語句不執(zhí)行
}
}
echo '循環(huán)結(jié)束';
?>
Continue語句
復制代碼 代碼如下:
for($a = 0; $a {
echo $a;
echo '
';
if($a ==5)
{
continue;//結(jié)束本次循環(huán)，繼續(xù)下次循環(huán)，循環(huán)后面的語句依然執(zhí)行
}
}
echo '循環(huán)結(jié)束';
?>
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