What to do if php trim doesn't work

Solution to php trim not working: First make trim accept parameters in reverse order; then use the "$post_Value = trim($str, "_");" statement to operate; finally pass "str_replace ” function can delete the label.

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Specific questions:

I'm trying to use trim to remove the underscore characters from the data returned in the $_POST array. I've tried using

 $post_Value= str_replace("_", " ", $key)

but the text doesn't seem to be returned as a single string. It is broken between each entry. Then I try to trim like this:

<?php
$connection = mysqli_connect(DB_SERVER, DB_USER, DB_PASS, DB_NAME);
 // Test if connection succeeded
 if (mysqli_connect_errno())
    {
    die("Database connection failed: " . mysqli_connect_error() . " (" .  mysqli_connect_errno() . ")");
}
 if (isset($_POST))
    {
    $str = "";
   foreach($_POST as $key => $value)
    {
    $str = $str . $key . ",";
    }
   $post_Value = trim("_", $str);
   }
   $query = "UPDATE player_match SET categoryOption=&#39;$$post_Value&#39; WHERE id=1";
 ?>

When I use the trim function nothing happens it doesn't remove the _ characters. My ultimate goal is to have a comma separated list as a single string in my database. Why doesn't my trim() function work in this case?

UPDATE: Found
given the page resource, so I had to do the following combination:

       $post_Value= str_replace("<br_/>", "", $str);
        $post_Value2= str_replace("_", " ", $post_Value);
        $post_Value3= rtrim($post_Value2,",submit,");
        echo $post_Value3;
        $query="UPDATE player_match SET categoryOption=&#39;$post_Value3&#39; WHERE   id=1";

Solution:

First , trim() accepts parameters in reverse order: $str;

then $character_mask.

So you should use: $post_Value = trim($str, "_");

Secondly, trim() does string processing on the string only at the beginning and end of the string . If the string is surrounded by non-shielded characters, no masking characters are removed from the string.

Actually you should use str_replace() with an empty replacement string (you've tried putting a space as a replacement):

$post_Value= str_replace("_", "", $key)

If you also want to remove the
tag ( In its typical variation), you can do this with a single str_replace() call, like this:

$post_Value= str_replace(array("_", "<br>", "<br/>", "<br />"), "", $key)

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