PHP几个比较常见的面试程序题整理

//反转字符串
function mb_strrev($str){
$len = mb_strlen($str,'utf-8');
$r = array();
for($i=0;$i<$len;$i++){
$r[] = mb_substr($str,$i,1,'utf-8');
}
return implode(array_reverse($r));
}

//得到url中扩展名
function getUrlExt($str){
$url_info = parse_url($str);
if(array_key_exists('path',$url_info)){
$path = $url_info['path'];
$file_info = pathinfo($path);
if(array_key_exists('extension',$file_info)){
return $file_info['extension'];
}
}
return false;
}

function get_rela_path($file_1,$file_2){
$array_1 = explode($file_1);
$array_2 = explode($file_2);
$rela = array_intersect_assoc($array_1,$array_2);
$length = count($rela);
if(count($array_2)-$length-1 == 0){
$a_r = array_fill(0,1,'.');
}else{
$a_r = array_fill(0,count($array_2)-$length-1,'..');
}
$b_r = array_slice($array_2,$length);
$a_res = array_merge($a_r,$b_r);
$str_res = implode('/',$a_res);
return $str_res;
}