PHP替换字符串(只替换首个字符串)

2. $str=preg_replace('/abc/','xyz',$str,1);
3. echo $str;

不用正则的字符串替换代码：

2. $replace='xyz';
3. if(($position=strpos($str,$replace))!==false){
4. $leng=strlen($replace);
5. $str=substr_replace($str,'xyz',$position,$leng);
6. }
7. echo $str;