php学习笔记之字符串常见操作总结

<?php
$str = "hello";
$str = 'hello';
>?

<?php
//heredoc的使用
$str3 = <<<MARK
hello
 world!
  ok;$a
   puzhong!
MARK;
echo $str3."<br/>";
//nowdoc的使用
$str4 = <<<'MARK'
hello
 world!
  ok;$a
   puzhong!
MARK;
echo $str4."<br/>";
?>

<?php
$str = "hello";
$str2 = "中国123";
echo strlen($str)."<br/>"; //输出5
echo strlen($str2)."<br/>";//输出9，utf8字符编码一个汉字占3个字节
echo mb_strlen($str2,"utf-8")."<br/>";//输出5，按照u8编码，计算字符的长度
?>

<?php
$str = "aAbBcdefgAa";
$char = "A";
echo strpos($str, $char)."<br/>";//输出1，区分大小写
echo stripos($str,$char)."<br/>";//输出0，不区分大小写
echo strrpos($str,$char)."<br/>";//输出9，区分大小写
echo strripos($str, $char)."<br/>";输出10，//不区分大小写
?>

<?php
$str = "hi,Fuck";
echo str_replace("fuck","fk",$str)."<br/>";//输出:hi,Fuck，区分大小写，所以没有找到要替换的内容
echo str_ireplace("fuck", "fk", $str)."<br/>";//输出:hi,fk，不区分大小写
$str = "男人，女人，男孩，女孩";
echo strtr($str, array("男"=>"女","女"=>"男"));//输出女人,男人,女孩,男孩
$str = "hello,webbc,wele";
echo substr_replace($str,"webxx",6,5);//输出hello,webxx,wele
?>

<?php
$str = "hello,webbc,wele!";
echo substr($str,6,5)."<br/>";//输出webbc
echo substr($str,6,-1)."<br/>";//输出webbc,wele，负数表示结束位置从后往前数
echo substr($str,-8,-1);//输出wele，负数表示起始位置从后往前数
?>

<?php
$str = "勇士,马刺,雷霆,快船,开拓者,小牛,灰熊,火箭";
$arr = explode(",",$str);
var_dump($arr);
/
输出array
  0 => string '勇士' (length=6)
  1 => string '马刺' (length=6)
  2 => string '雷霆' (length=6)
  3 => string '快船' (length=6)
  4 => string '开拓者' (length=9)
  5 => string '小牛' (length=6)
  6 => string '灰熊' (length=6)
  7 => string '火箭' (length=6)
/
echo implode($arr,"-");//输出勇士-马刺-雷霆-快船-开拓者-小牛-灰熊-火箭
?>

<?php
$str = "  hello world  ";
echo ltrim($str)."a"."<br/>";//输出:hello world a
echo "a".rtrim($str)."<br/>";//输出:a hello world
echo trim($str)."<br/>";//输出:hello world
?>

<?php
$str = "Is your ' name O'reilly?";
$a = addslashes($str);
echo $a;//输出Is your \' name O\'reilly?
echo stripslashes($a);//输出:Is your ' name O'reilly?

<?php
$str = "<b>我是加粗&nbsp;&nbsp;字体</b>";
echo $str; //输出我是加粗 字体
$htmlstr = htmlspecialchars($str);
echo $htmlstr;//输出<b>我是加粗&nbsp;&nbsp;字体</b>
echo htmlspecialchars_decode($htmlstr);//输出我是加粗 字体
?>

<?php
$str = 'name@example.';
echo strstr($str, '@'); //输出@example.
$str = 'This is a test';
echo substr_count($str, 'is'); //输出2
?>

<?php
$str = "i haVe a Dream";
echo strtolower($str)."<br/>";//输出i have a dream
echo strtoupper($str)."<br/>";//输出I HAVE A DREAM
echo ucfirst($str)."<br/>";//输出I haVe a Dream
echo ucwords($str)."<br/>";//输出I HaVe A Dream
?>