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    <p>In PHP, a variable or array element which has never been set is different from one whose value is <code>null</code>; attempting to access such an <em>unset</em> value is a runtime error. </p> <p>That's what you're running into: the array <code>$_POST</code> does not have any element at the index <code>"username"</code>, so the interpreter aborts your program before it ever gets to the nullity test.</p> <p>Fortunately, you can test for the existence of a variable or array element without actually trying to access it; that's what the special operator <code>isset</code> does:</p> <pre><code>if (isset($_POST["username"])) { $user = $_POST["username"]; echo $user; echo " is your username"; } else { $user = null; echo "no username supplied"; } </code></pre> <p>This looks like it will blow up in exactly the same way as your code, when PHP tries to get the value of <code>$_POST["username"]</code> to pass as an argument to the function <code>isset()</code>. However, <code>isset()</code> is not really a function at all, but special syntax recognized before the evaluation stage, so the PHP interpreter checks for the existence of the value without actually trying to retrieve it. </p> <p>It's also worth mentioning that as runtime errors go, a missing array index is considered a minor one (assigned the <code>E_NOTICE</code> level). If you change the <code>error_reporting</code> level so that notices are ignored, your original code will actually work as written, with the attempted array access returning <code>null</code>. But that's considered bad practice, especially for production code.</p> <p>Side note: PHP does string interpolation, so the <code>echo</code> statements in the <code>if</code> block can be combined into one:</p> <pre><code>echo "$user is your username"; </code></pre>
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    1. USMark Reed
    1. USMark Reed
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    1. COThank you. Very thorough but simple answer as to why I get this error and how to solve it. I didn't just want a "How to fix/get rid of this error" answer, I wanted to understand it and that is what you did for me, Thank you.
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      1. USXander Luciano
 

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