Video-03No.2PHP根本语法

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");
	
	/*
	 * 数据类型转换：强制转换
	 * gettype()：获取某个变量的类型，返回值是一个类型字符串
	 */
	$sum = 25.6;
	echo gettype($sum);
	$count = (int) $sum;
	echo gettype($count);
	echo ($count);
	echo ("
");
	echo ("
");
	
	/*
	 * settype(): 设置变量类型，返回值是一个boolean，是否设置成功
	 */
	echo ("
");
	$num1 = 100;
	echo settype($sum1, "string"); // boolean, integer, float, array, object, null
	echo ("
");
	echo $num1;
	echo ("
");
	echo ("----------------------------------");
	echo ("
");
	
	/*
	 * isset(变量名, 变量名..): 判断某个变量是否存在
	 * unset(变量名, 变量名...): 销毁某个变量
	 */
	$num2 = 12.58;
	$num3 = 12;
	echo isset($num2, $num3);
	echo isset($num3);
	unset($num2, $num3);
	echo isset($num2);
	echo isset($num1);
	echo isset($num1, $num3);
	echo ("
");
	echo ("----------------------------------");
	echo ("
");
	
	/**
	 * empty(变量名): 判断某个变量是否为空
	 * 若为空则返回1，非空则返回0
	 * null, 0, "", "0", false, array(), var $var以及没有任何属性对象都会被看成null
	 */
	$num4 = 12.4;
	$num5 = "";
	$num6 = (boolean)0;
	$num7 = null;	
	echo (empty($num4));
	echo (empty($num5));
	echo (empty($num6));
	echo (empty($num7));
	echo ("
");
	echo ("----------------------------------");
	echo ("
");
	
	/**
	 * 以上为判断是否属于变量是否属于某种类型
	 * 若是则返回ture，否则返回false
	 */
	echo is_double($num4);
	echo is_float($num4);
	echo is_int($num4);
	echo is_long($num4);
	echo is_null($num4);
	echo is_object($num4);
	echo is_array($num4);
	echo is_string($num4);
	echo ("
");
	echo ("----------------------------------");
	echo ("
");
	
	/*
	 * 临时转换变量
	 * intvar()、floatvar()、strvar() ：临时转换变量类型为int、float、string
	 */
	$num8 = 10.1;
	echo gettype($num8);
	echo intval($num8);
	echo gettype(intval($num8));
	echo floatval(intval($num8));
	echo gettype(floatval(intval($num8)));
	echo strval($num8);
	echo gettype(strval($num8));
	echo gettype($num8);
	echo ("
");
	echo ("----------------------------------");
	echo ("
");
	
	//定义常量,常量定义后其值不能在发生改变
	define("TOTAL", 23);
	echo TOTAL;
	
	//PHP预设常量,定义在phpinfo()函数里面
	echo phpinfo();
	echo ("
");
	echo  $_SERVER["SERVER_NAME"].":".$_SERVER["SERVER_PORT"];
	
?>

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?表单处理：

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";
	echo "您输入的密码是：".$pwd;

?>

 ： 在浏览器网页前台显示有效，后台源代码中显示无效
	 * 转义字符：在前台浏览器中显示无效。在后台源代码中显示有效
	 * 转义字符：
	 * 		\n : 换行符
	 * 		\r : 回车符
	 * 		\t : 水平制表符
	 * 		\\ : 反斜杠
	 *      \$ : 美元字符
	 *      \" : 双引字符
	 */
	$username = "shma";
	$username2 = "马韶华";
	echo "His name is $username";
	echo '
';
	echo 'His name is $username';
	echo "
";
	echo "他的名字是$username2，他已经23岁了！"; //无法显示
	echo "
";
	echo "他的名字是".$username2."，他已经23岁了！";
	echo "
";
	echo "他的名字是".$username2."，\n他已经23岁了！";
	echo "
";
	echo '他的名字是".$username2."，\n他已经23岁了！';
	
	/*
	 * == 与 ===
	 * != 与 !==
	 * 恒等表示只有两个操作数相等并且类型相同时才相等，或者不等
	 */
	$a = 6;
	$b = 5;
	$c = "5";
	echo '
';
	echo $a == $b;
	echo $a != $b;
	echo $a === $b;
	echo $a !== $b;
	echo $c === $b;
	echo $c == $b;
	
	// 错误抑制操作符 @
	
	$num = @(10/0);
	echo "$num";
	
	$value = 10;
	
	echo "value = ".($value > 1 ? $value : "0");
	
	// 数学运算
	
	/*
	 * + : 数字之间运算
	 * . : 字符串之间运算
	 */
	$a1 = 'a';
	$b1 = 5 .$a1;
	echo $b1;
	
	// is_numeric ― 检测变量是否为数字或数字字符串 
	$a = 123;
	
	if(is_numeric($a)) {
		echo $a."是数字";	
	} else {
		echo $a."不是数字";	
	}
	echo "
";
	
	// 获取随机数
	echo rand();
	echo "
";
	echo rand(1, 10);
	echo "
";
	echo mt_rand();
	echo "
";
	echo mt_rand(1, 10000);
	echo "
";
	echo getrandmax();
	echo "
";
	echo mt_getrandmax();
	
	//格式化数据
	$a = 10324.564343;
	echo "
";
	echo "
";
	echo number_format($a);
	echo number_format($a,2);
	echo number_format($a,2,"#", "!");
	
	//数学运算
	$b = -6.3;
	
	echo abs($b);
	echo min(1,3,4,5,6,-5);
	echo max(1,3,4,5,6,-5);
?>

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