<?php /**  * PHP 实现explort() 功能的详解  */ $str = ',1,2,3,4,321321,aaa,bbb'; function myExplode($seg,$str,$limit=0){    $_ret = array(0=>'');    $len = strlen($str);    $slen = strlen($seg);    $_limit = 0;    for($i=0; $i<$len; $i++){       if(substr($str,$i,$slen) == $seg ){           $_limit++;           $i += $slen-1;           continue;       }else{           $_ret[$_limit] .= $str[$i];       }    }    if($limit < 0 )       $_ret = array_slice($_ret, 0 , $limit );    else{       $_ret = $limit >= count($_ret) ? $_ret :  array_merge(array_slice($_ret, 0 , $limit-1 ), array(implode( $seg , array_slice($_ret,$limit-1))));    }    return $_ret; } var_dump(myExplode("4",$str)); echo "<br>"; var_dump(explode("4",$str)); echo "<br>"; ?>