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php和mysql web development (一) how to use php

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2016-06-23 14:35:31994browse

<?php/*双引号和单引号 * php中单引号里面内容默认它为字符串 * 所以在php中对于字符串尽量使用单引号*/$str='my name is ';$str1='$str jame green';$str2="$str jame green";$str3=$str.'jame green';echo $str1. '<br/>';//无效的拼接 输出$str jame greenecho $str2. '<br/>';//my name is jame greenecho $str3. '<br/>';//my name is jame green/*php中的变量类型 * integer float string boolean array object *  */$int_val=1;$float_val=0.1;$string_val='my name is mrwu';$boolean_val=true;$array_val=array('name'=>'my name is mrwu');class class_val{}$class_val=new class_val();//object/* * 可变变量 */$varname='name';$$varname='jame green';echo $name. '<br/>';//output jame green;/** * 超级全局变量 * $_REQUEST, $_POST,$_COOKIE,$_FILES,$EVN,$_GET *//* * 算数操作符 +-*.... */$b=6+($a=5);echo $b. '<br/>';//11 先赋值 然后计算echo $b++. '<br/>';//11 这时候b=12echo ++$b. '<br/>';//13$a=&$b;$b=11;echo $a. '<br/>';//11 a是b变量的别名//比较操作符unset($a);unset($b);$a=0;$b='0';//var_dump($a==$b);//var_dump($a === $b);var_dump(false == FALSE);//truevar_dump(false === FALSE);//truevar_dump(false == 0);//truevar_dump(false === 0);//falsevar_dump(false == '');//truevar_dump(false === '');//falsevar_dump(false == "");//truevar_dump(false === "");//falsevar_dump(false == null);//truevar_dump(false === null);//falsevar_dump(false == '0');//truevar_dump(false === '0');//falsevar_dump(false == 00 );//truevar_dump(false === 00 );//falsevar_dump(false == NULL);//truevar_dump(false === NULL);//false/** * ? : @ */$a=5;$b=6;$c = $a > $b ? $a : $b;$d=@(1 / 0);//屏蔽错误信息ini_set('track_errors', 1); echo $php_errormsg;//没有输出/* * 数组运算 */$a=array(1,2,3);$b=array(2,3,4);var_dump($a == $b);var_dump($a != $b);/* * 执行操作符 */$out=`dir c:`;echo $out. '<br/>';/* * instanceof */var_dump($class_val instanceof class_val);//true/* * 测试和设置变量类型 set_type();gettype();intval(); *//* *if elseif while continue break switch ...*/

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