How to remove one instance of one string in PHP?

Question

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

<br />

tag at 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.

But what if the user inserts blank spaces before the br? Is it possible? If yes, see stackoverflow.com/questions/2514002/… — Nicolò Martini
– Nicolò Martini, Commented Mar 25, 2010 at 9:02

Boldewyn · Accepted Answer · 2010-03-25 08:45:21Z

4

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']);

edited Mar 25, 2010 at 8:45

answered Mar 25, 2010 at 8:39

Boldewyn

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5 Comments

Boldewyn Over a year ago

Oh, how I miss Python's startswith() method in PHP!

poke Over a year ago

You copied the misplaced closing parenthesis from the question.

nikc.org Over a year ago

@Boldewyn: what keeps you from creating one? I do for my personal projects.

Boldewyn Over a year ago

@nikc: I do, too, but still, a default implementation would be a nice extension, particularly with respect to the tons of other functions of less use PHP pumps into the global namespace.

nikc.org Over a year ago

@Boldewyn: I agree completely. str_startswith and str_endswith should exist.

poke · Accepted Answer · 2010-03-25 08:39:46Z

3

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

answered Mar 25, 2010 at 8:39

poke

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Comments

animuson · Accepted Answer · 2010-03-25 08:40:23Z

3

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?

answered Mar 25, 2010 at 8:40

animuson♦

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1 Comment

Boldewyn Over a year ago

Let me tell from my experience: It depends. If the editor has this and only this quirk, fixing server-side is a) faster to implement and b) future proof. The problem is, that you have to port fixes to the editor to each new version of the editor you include. In the above case, however, stripping a <br> from the beginning of a string is a reasonable sanitation plus you don't have the fuss when updating the editor software.

reko_t · Accepted Answer · 2010-03-25 08:39:30Z

2

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);

answered Mar 25, 2010 at 8:39

reko_t

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1 Comment

Carson Myers Over a year ago

couldn't you just use preg_match and add an end-of-string anchor after the <br />? Like preg_match('#^<br />$#')

Felix · Accepted Answer · 2010-03-25 08:42:07Z

1

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.

answered Mar 25, 2010 at 8:42

Felix

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1 Comment

nikc.org Over a year ago

Depends on the use case if it is a realistic scenario, but if the content is just an image, this approach will fail.

Nicolò Martini · Accepted Answer · 2010-03-25 08:51:43Z

0

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.

answered Mar 25, 2010 at 8:51

Nicolò Martini

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