Freemember parsing error

Question

Currently using EE 2.7.3 and Freemember 2.3.1. I made sure to create an encryption key first for my config file. I've followed the documentation so far, it's thorough and keeps things minimal. Unfortunately, immediately after calling Freemember I'm being given this error:

Parse error: syntax error, unexpected ':' in /home/.../system/expressionengine/third_party/freemember/mod.freemember.php on line 397

This is line 397 of mod.freemember.php:

$return_url = ee()->input->get_post('return_url') ?: $this->history(0);

And here is my login markup:

{if logged_out}
    <a href="#" class="login">Login</a>
    <div id="login-modal">
            {exp:freemember:login return="PREVIOUS_URL"}
                <input type="text" name="username" value="" maxlength="32" placeholder="Username">
                <input type="password" name="password" value="" maxlength="32" placeholder="Password" autocomplete="false">
                <input type="submit" name="submit" value="Submit">
                {if auto_login}
                    <p><input type="checkbox" name="auto_login" value="1" {auto_login_checked} > Auto-login on future visits</p>
                {/if}
                <a href="{path='member/forgot_password'}">Forgot your password?</a>
            {/exp:freemember:login}
    </div>
{/if}
{if logged_in}
    <a class="login" href="{exp:freemember:logout_url}">Logout</a>
{/if}

div#login-modal is being toggled with JQuery (1.10.4)

What is causing this? My guess is I've overlooked something but I'm out of ideas.

EDIT: Trying to isolate the issue, any hint of Freemember tags on the page will return an error.

Answer 1

That syntax you pointed out on line 397 is PHP 5.3 only. You are likely on an older version of PHP.