PHP String Replace/Append - php

Question

I am trying out a Logic in strings but facing difficulties in string manipulation functions. Which function will be good for this below approach:
My String is "Hello" I want to add "------------------" after the first string that is "Hello--------------" and the length of the string should be 20 after the string manipulation.
I want to add "------------------" to the string to make it 20 length.
In other words: Hello+Underscores
If the string length is too much we can trim the string.
Below is the code which I tried.
<?php
$challenge = 'hello';
$length = strlen($challenge);
$i= $length +1;
$challenge=substr($challenge,0,$i);
echo $challenge.'<br>';
?>
I tried string concatenation but I am sure I cant use it in this logic, I think the string adding should be done with preg_replace.
Can some one give a good advice on it!

Answer 1

str-pad is the easiest way to achieve your task and code sample as follows.
<?php
$input = "Alien";
echo str_pad($input, 10); // produces "Alien "
echo str_pad($input, 10, "-=", STR_PAD_LEFT); // produces "-=-=-Alien"
echo str_pad($input, 10, "_", STR_PAD_BOTH); // produces "__Alien___"
echo str_pad($input, 6 , "___"); // produces "Alien_"
?>

Answer 2

Just use str_pad.
$input = 'hello';
$output = str_pad($input, 20, '_');
echo $output;
demo: http://ideone.com/0EPoV2

Answer 3

Here you go
<?php
$string = "anything";
echo substr($string."------------------------------------------",0,20);
?>
Just use the first 20 chars of your string and ------------------------
Edit based on new requirement not given in original question for some reason.
<?php
$string = "anything";
$newstring = substr($string."------------------------------------------",0,20);
echo $newstring."whatever you want to add at end";
?>

Answer 4

Try this
<?php
$input = "HELLO";
echo str_pad($input, 10, "----", STR_PAD_RIGHT);
?>
here $input is string and 10 is length of char added STR_PAD_RIGHT is position
View this link PHP.net

Answer 5

$str = 'Hello';
$str .= "_";
while(strlen($str) <= 20){
$str .= "-";
}
echo $str;

Answer 6

try this code
$challenge = 'hello';
$length = strlen($challenge);
if($length < 20){
$limit = 20-$length;
for($i=0;$i<$limit;$i++){
$challenge .= '_';
}
}
echo $challenge;