PHP——字符串

<?php
    //strlen("aaa");取字符串的长度 ***
    echo strlen("aaaaa");
          echo "<br />";
    //$array = explode("|",$s);拆分字符串，返回一个字符串的数组 ***
    $str1="aaaa|bbb|cc|d";
    $array1=explode("|",$str1);
    print_r($array1);
          echo "<br />";
    print_r(explode("|",$str1));
          echo "<br />";
    //$s = substr($s,4,10);截取字符串，根据开始位置结束位置截取 ***
    $str2="hello world";
    echo substr($str2,2,3); 
          echo "<br />"; 
    //strcmp("aaa","aaa");比较两个字符串，相同的话输出0，不相同输出-1
        //区分大小写
    echo strcmp("aaa","bbb");//-1
         echo "<br />";
    echo strcmp("aaa","aaa");//0
         echo "<br />";
    //strcasecmp("aaa","AAA");比较两个字符串，不区分大小写
    echo strcasecmp("aa","AA");
         echo "<br />";
    //strtolower("AbCdEfGh")；转小写
    echo strtolower("AAAAAABBbb");
         echo "<br />";
    //strtoupper();转大写
    echo strtoupper("akjhajkdhfjk");
         echo "<br />";
    //$s = implode($array);将数组转为字符串
    echo implode($array1);
         echo "<br />";
    //$s = substr_replace($s,"china",1,2);通过位置替换字符串
    $str3=substr_replace($str2,"你好",0,1);
    echo $str3;
         echo "<br />";
    //$s = str_replace("l","dog",$s);替换字符串，相当于记事本中的查找替换
    $str4=str_replace("l","你过来",$str3);
    echo $str4;

?>