creating a find and replace application in php - php

Question

i have a php code :
<?php
$offset=0;
if(isset($_POST['text']) && isset($_POST['searchfor']) && isset($_POST['replacewith']))
{
$text=$_POST['text'];
$search=$_POST['searchfor'];
$replace=$_POST['replacewith'];
$search_length=strlen($search);
if(!empty($text)&&!empty($search)&&!empty($replace))
{
while($strpos=strpos($text,$search,$offset))
{
$offset=$strpos + $search_length;
$text=substr_replace($text,$replace,$strpos,$search_length);
}
echo $text;
}
else
{
echo 'pls fill in all fields';
}
}
?>
<form action='string_search.php' method='POST'>
<textarea name='text' rows='6' cols='30'></textarea><br><br>
Search For:
<input type='text' name='searchfor'><br><br>
Replace with:
<input type='text' name='replacewith'><br><br>
<input type='submit' value='find and replace'>
</form>
When i type a string.Forexample 'i found my dog' in textarea and search for 'dog' in 'search for' then replace with 'cat' in 'replace' then submit it will out put 'i found my cat'.However it always output the original string ('i found my dog').I don't know why ?

Answer 1

Why do you use:
while($strpos=strpos($text,$search,$offset)) {
$offset=$strpos + $search_length;
$text=substr_replace($text,$replace,$strpos,$search_length);
}
echo $text;
??
I think its the same if you just use:
$strpos=strpos($text,$search);
$text=substr_replace($text,$replace,$strpos,$search_length);
echo $text;
And probably is your while who is doing the bad work. I don't know, it's a suggestion. With this, your code should work.

Answer 2

<?php
$offset = 0;
if (isset($_POST['user_input_box']) && isset($_POST['search']) && isset($_POST['replace'])) {
$user_input_box = $_POST['user_input_box'];
$search = $_POST['search'];
$replace =$_POST['replace'];
//To check whether above code work or not
// echo $user_input_box = $_POST['user_input_box'];
// echo $search = $_POST['search'];
// echo $replace = $_POST['replace'];
$search_length = strlen($search);
if (!empty($_POST['user_input_box']) && !empty($_POST['search']) && !empty($_POST['replace'])) {
while ($string_position=strpos($user_input_box, $search ,$offset)) {
// to check while and strpos
// echo $string_position."<br>";
// echo $offset = $string_position + $search_length;
$offset = $string_position + $search_length;
$user_input_box = substr_replace($user_input_box, $replace,$string_position,$search_length );
}
echo $user_input_box;
}
else{
echo "Please fill the complete fields.";
}
}
?>
<form method="POST" action="eleven0.php">
<textarea cols="34" rows="12" name="user_input_box"></textarea>
<br><br>
<label>Search For: </label> <br>
<input type="text" name="search"><br><br>
<label>Replace With: </label><br>
<input type="text" name="replace"><br><br>
<input type="submit" value="Find and Replace">
</form>