How to remove one instance of one string in PHP?

I have a open source editor on the cms that I am making that automatically inserts a

<br />

tag at 开发者_如何学编程the beginning of the post it submits to the database. This makes validation a pain, since even though there is no real text being submitted, the form still accepts the break tag as input and prevents the "Please enter some text" error from showing.

So I tried to remove the opening break tag by filtering my input like this:

substr($_POST['content'], 6);

This works as long as the user doesn't press the backspace a couple of times which removes the break tag in which case the first 8 characters of the post gets removed even if they are not a break tag.

So how can I remove the first 6 characters of the input ONLY if those first 6 characters are composed of the break tag. Also I don't want to remove all break tags, only the one at the very beginning of the post.

Performant and verbose:

if (substr($_POST['content'], 0, 6) == '<br />') {
    $_POST['content'] = substr($_POST['content'], 6);
}

Not so verbose, but slightly slower:

$_POST['content'] = preg_replace('#^<br />#', '', $_POST['content']);

$content = $_POST['content'];
if ( substr($content, 0, 6) == '<br />' )
    $content = substr($content, 6);

Creating a workaround for your open source editor is not the solution you should be seeking. Wouldn't it be wiser to just fix the editor so it doesn't insert that <br /> there so you just don't have to worry about it at all?

You can use eg. preg_replace:

$text = preg_replace('#^<br />#', '', $text);

If you don't want to use regexps, you could check with substr before removing:

if (substr($text, 0, 6) == '<br />')
    $text = substr($text, 6);

Here's what I think to be a better solution of testing whether the user has actually entered something:

if (!strlen(trim(strip_tags($_POST['content'])))) {
    // no content
}
else {
    // some content
}

This basically tests if there is anything other than HTML tags in the input.

First remove blank spaces at the beginning with ltrim, then test if there is a br. If there is a br remove it and do another ltrim to remove blanks after the br.

$str = ltrim($_POST['content']);
if (substr($str, 0, 6) == '<br />'){
   $str = ltrim(substr($str, 6)); 
}

if ($str){
    //some content
} else {
    //no content
}

In this way you ignore blank spaces and new lines before and after the br.