在字符串中第一个字符后插入字符？

$var = "Hello";

How can I insert the character : in after the first character of the string above ? The first character could be anything. So I want to do something like

$res = add("Hello");
echo $res; // which return H:ello

I know how to do this through str_replace but this needs the first character to be always the same..

Any help would be highly appreciated

you can use string append and substr to do it

  $var = $var[0].":".substr($var,1);

$newstr = substr_replace($oldstr, $str_to_insert, $pos, 0);

http://www.php.net/manual/en/function.substr-replace.php

$str = substr($str, 0, 1) . ':' . substr($str, 1)

In PHP I would probably try this:

$string = "Hello";
$new_string = substr($string,0,1) . ":" . substr($string,1,$strlen($string)-1);

This would get H (= first char) + : (= fixed char) + ello (= the rest of the string)

<?php 
    function addColon($myString){
     return $myString = substr($myString, 0, 1) . ':' . substr($myString, 1);
    }

    echo addColon("Hello");
?>