PHP基础 字符串

<?php
  $username="ginoSin";
  #判断参数是否只在a-z范围
  if(ereg("([^a-z])",$username))
  {
          echo "username must be all lowercase";
  }
  else
  {
          echo "username is all lowercase";
  }
  echo "<br>";

  #输出字符参数的长度
  echo "the length of $username is:".strlen($username);

  #比较字符与参数是否相等，区分大小写比较strcmp(),不区分大小写strcasecmp()
  if(strcmp($username,"ginosin")!=0)
  {
            echo "<br>that is equal!";
  }

  #求两个字符相同的部分的长度 strspn()，不同的部分strcspn()
   echo "<br>".strspn($username,"ginoEnn");

  #转换成小写 strtolower
  #转换成大写 strtoupper
  #第一个字符大写 ucfirst()
  #每个单词变为大写 ucwords()

  #nl2br()将\n转换为br
  $recipe="<br>"."one day,
  i remember to buy
  a book of php";
  echo nl2br($recipe);

  #htmlentities() 特殊字符等价转换成html
  #htmlspecialchars()
  #get_html_translation_table()
  #array_flip()反转特殊字符

  #自定义转换 strtr
   $table=array("<b>"=>"<strong>","</b>"=>"</strong>");
   $html="<b>No smoking</b>";
   echo "<p>".strtr($html,$table)."</p>";

  #html转换成纯文本,去掉html标签 strip_tags()
   $input="<a href='http://cnblogs.com/tomieric'>tomieric</a> Document.";
   echo strip_tags($input); //去掉所有标签
   echo strip_tags($input,"<a>"); //只去掉a

  #分解字符串 explode(),split()
  echo "<p>";
  $newstr=explode(" ","i'm a geek");
  //print_r $newstr
  echo "</p>";

  #将数组转换为字符串implode
   $goods=array("banana","apple","pear");
   echo "<p>".implode(";",$goods)."</p>";

  #strpos(str,substr[,int offset])区分大小写查找substr第一次出现
  #strrpos()最后一次出现

  #查找替换
  $author="tomieric@gmail.com";
  $author=str_replace("@","(at)",$author);
  echo "<p>".$author."</p>";

  #从某字符开始截取后面的部分
   $author="tomieric@gmail.com";
   //echo "<p>".ltrim(strstr($author,"@"),"@")."</p>";   //output "gmail.com"
   echo "<p>".strstr($author,"@")."</p>";  //output "@gmail.com"

  #预定位置截取字符串 substr(str,start[,length])
   echo "<p>".substr($author,0,8)."</p>";

  #substr_count(str,substring) 确定字符串出现频率

  #替换substr_replace(str,replacement,start[,length])
  $phoneNumber="15952341523";
  echo "<p>".substr_replace($phoneNumber,"135",0,3)."</p>";

  #ltrim(str,charlist) 从字符开始处截取
   ltrim($email,"@");  //return gmail.com
  
  #rtrim(str,charlist) 从字符右侧开始截取
   rtrim($emai,"@");   //return tomieric
  
  #trim(str,charlist) 从两侧截取

  #str_pad(str,length,type) 填充 默认空格填充

  #count_chars(str,[,mode])字符统计 
  #str_word_count(str,[,format])单词统计
?>