PHP基础

1.  输出 echo 或 print 

<?php
    echo "hello"; 
?>

<?php
    echo 13*123;
?>

<?php
    print "hello";
?>

2. 变量，$开头

<?php $myVariable=0 ; ?>

3 . 注释 : // 同  c, java

4. if else elseif: 基本同C  Java, 但是elseif连写

if ()
{}
elseif ()
{} 
else
{}

5. 数组 array

$items=array("apple","banana"); //创建数组

echo $items[2];// 输出数组元素

unset($items);
unset($items[2]);// 删除元素或整个数组

array_push($items,"pig"); // push

count($items);// count

sort($items); // sort

  associative array：  类似于python的字典，c++的map

$myAssocArray = array('year' => 2012, 'colour' => 'blue',  'doors' => 5);

echo $myAssocArray['colour'];//输出

using  for each in associative array

 $food=array("apple"=>"yes","banana"=>"no","pig"=>"yes");
 
foreach($food as $f =>$isYes)
{
     echo $isYes. '  '.$f.'<br >';
}

6. for 循环：同C Java

7. foreach

$items= array("JavaScript", "HTML/CSS", "PHP","Python","Ruby");
        
foreach ($items as $i) 
{
      echo "<li>$i</li>";
}

  

8. while/ do while： 同 C Java

9. 函数 function

function foo($pa1, $pa2)
{
return "xx";
}

10. 类 class

class Person
{
     public $name;
     public $age;
     public function __construct($na)//构造函数
    {
         $this->name=$na;//访问成员变量前不加"$"
    }
}
            
$student=new Person("student");//创建实例
    

is_a($me, "Person");// 判断是否是某个类

property_exists($me, "name");//  判断是否有某个property

method_exists($me, "dance");// 判断是否有某个method

class Person
{
    public static function say()// 静态函数
    {
        echo "Hello!";
    }
    const name="xxx";//常量
}


Person::say();
Person::name;//调用静态函数和常量

 11. triple equal 

double equal only compare value but ignore type

triple equal will compare both

<?php
$num1 = "1";
$num2 = 1;
if ($num1 === $num2){
    echo "type and value equal";
}
elseif($num1 == $num2){
    echo "value equal";
}
?>