如何判断用户是否在表单条目中输入了http：// [复制]

I have a form allowing users to enter in their referral link (URL). I need to be sure they entered the http:// first before the url. If they entered it then it's ok, if they did not enter it then I need to add it before placing the url in the database.

How can I check this in PHP before saving the form in the database?

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Use substr (and don't forget "https://" and "//") :

<?php
$url = 'example.com'; // Here is the URL you got in input
if (substr($url, 0, 7) != 'http://' && substr($url, 0, 8) != 'https://')
    $url = 'http://'.$url;
else if (substr($url, 0, 2) == '//') // "//" is valid, it just means that the browser needs to continue using http or https depending on what it is currently using
    $url = 'http:'.$url;