if http:// is in string then leave it, else if not add it

I have a input that you enter a URL, i basically want to write 开发者_如何学Csome php that says if the domain containts "http://" then leave it be, else if not then add it to the beginning. This is what I have so far...

$domain = $_POST["domain"];

if (strpos($domain, "http://")) {
return $domain;
} else {
$domain = "http://" . $domain;
}

This doesnt seem to work..

it doesnt add the http:// on if it doesnt contain http://.

you forgot to return $domain.

$domain = $_POST["domain"];

if (strpos($domain, "http://") !== false) {
return $domain;
} else {
return "http://" . $domain;
}

Since the string starts with http://, strpos will return 0, which will evaluate to false.

Change the if statement to:

if(strpos($domain, "http://") !== FALSE){

"http://" then leave it be, else if not then add it to the beginning.

How about adding adding it regardless? I find that to be easier:

<?php
$url = 'http://www.google.com';
echo 'http://' . preg_replace( '~^http://~', '', $url );

read manual:

This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.

That is because strpos will return the location of the string, within the string. In your url, that is 0. Which equals to false. Make it a strict check - add === false.

if (strpos($domain, "http://") !== false) {
//return substr($domain,7); Thanks Rocket. 
return $domain;
} else {
return "http://" . $domain;
}

I know this is a bit late to the party, but I prefer this approach:

if (!preg_match('#^http[s]{0,1}://#', $input)) {
    $input = 'http://' . $input;
}

This will preserve a https:// address, and not have you ending up with http://https://www.mysite.com. You could also further edit it to strip out https:// if you had a rule for not using https addresses.

I know the original question didn't ask for this, but I think it's important to consider in most situations, and will hopefully help someone else who comes looking.

Use caution when using strpos(). It will return 0 when 'http://' is found at the beginning of the string, causing your if statement to fail unexpectedly. You will want to check the type of the return to be sure:

$domain = $_POST["domain"];

if (FALSE !== strpos($domain, "http://")) {
    return $domain;
} else {
    return "http://" . $domain;
}