如果http：//在字符串中则保留，否则如果不添加它

I have a input that you enter a URL, i basically want to write some 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://.

"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.

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){

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.

you forgot to return $domain.

$domain = $_POST["domain"];

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

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;
}

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.