Php笔记-基础语法

发表于

变量

php 的变量必须用$开头

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$myAge

switch语法

switch有两种语法：

  • 正常的语法：
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<?php
        $myAge = 25;
        switch($myAge){
            case 20:
                print "your are age is 20";
                break;
            case 24:
                print "your are age is 24";
                break;
            case 25:
                print "your are age is 25";
                break;
            default:
                print "your are age is not match";
                break;
      
        }
  • sugar语法：
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<?php
        $myAge = 25;
        switch($myAge):
            case 20:
                print "your are age is 20";
                break;
            case 24:
                print "your are age is 24";
                break;
            case 25:
                print "your are age is 25";
                break;
            default:
                print "your are age is not match";
                break;
        endswitch;
    ?>

数组

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$array = array("cheng", "fang", "peng");

获取数组的值有两种方法

  • 通过[]
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$array[2]；
  • 通过{}
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$array{2}

数组中删除元素

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unset(array[2]);
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<?php
       $languages = array("HTML/CSS",
       "JavaScript", "PHP", "Python", "Ruby");
     
       unset($languages[3]);
                   
       foreach($languages as $lang) {
         print "<p>$lang</p>";
       }
       />

for循环

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<?php
       // 输出前五个偶数
       for ($i = 2; $i < 11; $i = $i + 2) {
         echo $i;
       }
     ?>

foreach循环

foreach循环是迭代对象里的每一个元素。

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<?php
         $langs = array("JavaScript",
         "HTML/CSS", "PHP",
         "Python", "Ruby");
       
         foreach ($langs as $lang) {
             echo "<li>$lang</li>";
         }
       
         unset($lang);
       ?>

while 循环

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<?php
	$headCount = 0;
	$flipCount = 0;
	while ($headCount < 3) {
		$flip = rand(0,1);
		$flipCount ++;
		if ($flip){
			$headCount ++;
			echo "<div class=\"coin\">H</div>";
		}
		else {
			$headCount = 0;
			echo "<div class=\"coin\">T</div>";
		}
	}
	echo "<p>It took {$flipCount} flips!</p>";
	?>

endwhile的使用

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<?php
	 $isLoop = true;
	 $index = 0;
    while($isLoop):
        if($index > 10){
            $isLoop = false;
            }
            echo $index;
            $index++;
    endwhile;
        ?>

do-while的使用

先执行do中的代码，然后再执行while循环

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<?php
	$flipCount = 0;
	do {
		$flip = rand(0,1);
		$flipCount ++;
		if ($flip){
			echo "<div class=\"coin\">H</div>";
		}
		else {
			echo "<div class=\"coin\">T</div>";
		}
	} while ($flip);
	$verb = "were";
	$last = "flips";
	if ($flipCount == 1) {
		$verb = "was";
		$last = "flip";
	}
	echo "<p>There {$verb} {$flipCount} {$last}!</p>";
	?>

函数

字符串内建函数

  • strlen 返回字符串的长度
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<?php
       $name = "chengfangpeng";
       print strlen($name);
   ?>
  • substr 截取字符串函数，返回截取到的子字符串
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<?php
     $name = "chengfangpeng";
   print substr($name, 5, 10);
  ?>
  • strtoupper 将字符串转为大写
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<?php

   $name = "chengfangpeng";
   print strtoupper($name);
   ?>
  • strtolower 将字符串转为小写
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<?php
  $name = "CHENGFANGPENG";
  print strtolower($name);
  ?>
  • strpos 找出字符串中某个子字符串的位置，如果没有所给的字符串，返回false，否则返回子字符串在原字符串中的位置。
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<?php
  
   $name = "chengfangpeng";
   print strpos($name, "fang");
   
if(strpos($name, "Hello") === false){
       print "no match string";
   }
   ?>

数学内建函数

  • round 将一个float类型的数，四舍五入为整形，如果再传入保留位数参数可以转化成保留小数位的float类型。
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<?php
     print round(M_PI); //3
     print round(M_PI, 3);//3.142
   ?>
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//使用rand，strlen，substr函数随机打印你姓名中的一个字母
 <?php
  
    $name = "chengfangpeng";
    $rIndex = rand(0, strlen($name));
    print substr($name, $rIndex, 1);
    ?>