动态网页技术PHP程序字符串处理函数

动态网页技术PHP程序字符串处理函数(4)         $n = strlen($substr );
        $x = strlen($newsubstr );
        if (strchr($str, $substr ) == false) return false;
        for ( $i=0; $i<=($m- $n+1); $i++){
                 $i = strchr($str,  $substr);
                $str = str_delete ($str, $i, $n);
                $str = str_insert($str,  $i, $newstr);
        }
        return $str ;
}
?>

<?php
//--------------------
// 自实现字符串处理函数
//--------------------

//插入一段字符串
function str_insert($str, $i , $substr)
{
        for($j=0 ; $j<$i; $j ++){
                $startstr .= $str[$j ];
        }
        for ($j=$i; $j <strlen($str); $j ++){
                $laststr .= $str[$j ];
        }
        $str = ($startstr . $substr  . $laststr);
        return $str ;
}

//删除一段字符串
function str_delete($str , $i, $j)
{
        for ( $c=0; $c<$i;  $C++){
                $startstr .= $str [$c];