PHP学习笔记

PHP入门

php的四种不同的风格

<?php 代码 ?>
官方推荐风格
<? 代码 ?>
短标记风格，需配置文件php.ini中开启short+open_tag
<% 代码 %>
ASP风格，需配置文件php.ini中开启asp_tags
<script language=”php”> 代码 </script>
JavaScript标记的风格，这种风格在任何情况下都可以使用。

字符串

单引号

变量和转义序列都不会进行转义

双引号

PHP会处理双引号括起来的字符串、变量以及转义序列。

<?php
//demo
	$a = "双引号";
	echo "{$a}引起来的字符串进行转义
";
	$b = '单引号';
	echo '$b引起来的字符串不进行转义
';
	echo "
";
	echo "$a,Hello";
?>

这里要注意字符串里面如果需要使用变量的话需要用{}将变量括起来，或者在变量后面加一些符号，与后面的字符隔开。

字符串切片

<?php
//demo
	$s = 'PHP is the best language in the world!';
	echo substr($s,0)."
";
	echo substr($s,0,6)."
";
	echo substr($s,-6,6)."
";
	echo substr($s,2,-6)."
;";
?>

字符串查找

<?php
//demo
	$s = 'PHP is the best language in the world! Php in my favorite! I just say PHP.';
	echo "字符串长度为：" . strlen($s) . "
";
	echo "PHP出现了" . substr_count($s,"PHP") . "次
";
	echo strstr($s,"Php") . "
";
	echo stristr($s, "Php") . "
:";   //匹配时不区分大小写
	echo stripos($s , "PHP") . "
";    //返回第一次匹配中的位置
?>

字符串替换

<?php
//demo
	$s = 'PHP is the best language in the world!';
	echo substr_replace($s, 'python', 0,3);
	
?>

正则

参考文档

数组

组成

数组由键值对组成，键可以是数字，也可以是字符。

<?php
//demo
	$arr = array(2 => "a" , 3 => "c" , "this" => 'that');
	echo '数组元素个数：' .count($arr)."
原数组:";      //数组键值对个数
	print_r($arr);        //打印数组
	echo "
ksort:";
	ksort($arr);
	print_r($arr);        //ksort按键从小到大排序
	echo "
asort:";
	asort($arr);         //asort按数值从小到大排序
	print_r($arr);
	echo "
sort:";
	sort($arr);          //sort按数值从小到大排序
	print_r($arr);
	echo "
rsort:";
	rsort($arr);         //rsort按索引从小到大排序
	print_r($arr);
	echo "
";
?>

数组操作符

• 使用+操作符号时，如果两个数组有相同的键，将不会添加。

<?php
//demo
	$arr1 = array('1' => 1, '2' => 2, '3' => 3, '4' => 4 );
	$arr2 = array('45' => 123, '6' => 8 );
	$arr3 = array('1' => 4, '6' => 2);
	var_dump($arr1 + $arr2);
	echo "
";
	var_dump($arr1 + $arr3)
?>

访问数组

<?php
//demo
	$r = range('a','z');
	foreach ($r as $value) {
		echo "$value";
	}
	echo "
=====================
";
	foreach ($r as $key => $value) {
		echo "$key=>$value ";
	}
	echo "
$r[5]";
?>

数组的创建与添加

<?php
//demo
	$r = array('PHP' , "python" , "C" , "Java" , "C++" );
	print_r($r);echo "
";
	$r[] = "Perl";
	print_r($r);echo "
";
	$r[8] = "Ruby";
	print_r($r);echo "
";
	$t = array('a' => "PHP" , "b" => "Python" , "c" => "C++" , "d" => "C++");
	print_r($t);
?>

数组元素的添加与删除

<?php
$r = array("PHP","Python","C","Java","C++");
print_r($r);echo "
";
array_unshift($r,"Ruby","Perl");    //在数组头部添加
print_r($r);echo "
";
array_push($r,"Go");                //在数组尾部添加
print_r($r);echo "
";
array_shift($r);                    //删除数组第一个元素
print_r($r);echo "
";
array_pop($r);                      //删除数组第一个元素
print_r($r);echo "
";
?>

数组与字符串互转

<?php
$r = array('PHP',"Python","Perl");
echo "初始化";print_r($r);echo "
";
$r = implode('==',$r);
echo "After implode:  ";print_r($r);echo "
";
$r = explode("==",$r);
echo "After explode:  ";print_r($r);echo "
";
?>

in_array()判断键是否在数组中

<?php
$r = array("a" => 'PHP',"b" => "Python","c" => "Perl");
if (in_array('PHP', $r)) echo "PHP in array(r)";
else echo "PHP not in array(r)";
?>

array_merge()合并数组

<?php
$r = array("a" => 'PHP',"b" => "Python","c" => "Perl");
$t = array("d" => "C" , "a" => "Go");         //这里的a会将原来的a覆盖掉
$n = array_merge($r,$t);
print_r($n);
?>

array_combine()

<?php
$r = array("a" => 'PHP',"b" => "Python","c" => "Perl");
$t = array("1" => "a" , "2" => "b" , '3' => 'c');
$n = array_combine($r,$t);
print_r($n);
?>

extrace()将数组转换成标量变量

<?php
$r = array("a" => 'PHP',"b" => "Python","c" => "Perl");
extract($r);
echo $a;echo "
";
echo $b;echo "
";
echo $c;echo "
";
?>

array_keys()和array_values()

<?php
$r = array("a" => 'PHP',"b" => "Python","c" => "Perl");
print_r(arrat_keys($r));
echo "
";
print_r(array_values($r));
echo "
";
?>