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POis_null($x) vs $x === null in PHP
 

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    <blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/4662588/whats-the-difference-between-is-nullvar-and-var-null">What&#39;s the difference between is_null($var) and ($var === null)?</a> </p> </blockquote> <p>PHP has two (that I know of, and three if you count <code>isset()</code>) methods to determine if a value is null: <code>is_null()</code> and <code>=== null</code>. I have heard, but not confirmed, that <code>=== null</code> is faster, but in a code review someone strongly suggested that I use <code>is_null()</code> instead as it is specifically designed for the null-evaluation purpose. He also started talking about math or something.</p> <p>Anyway, the fact that <code>is_null()</code> is apparently slower also leads me to believe that it's doing more than <code>=== null</code> does and is probably preferred. Is there any reason to use one or the other? Is one always preferred? What about <code>isset()</code>?</p> <p>As an addendum to possibly not get this question closed, what about <code>isset()</code> vs. <code>is_null()</code>? It seems that all <code>isset()</code> will do is suppress the notice, so unless you actually <em>want</em> a notice for an undefined variable, any reason to use <code>is_null()</code> instead? How about if you know the variable is initialized at the time?</p> <p>Finally, is there any mathematical reason to prefer <code>is_null()</code> over <code>=== null</code>? Something about null not being comparable?</p>
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    1. COGood question, but as far as I've learned, these kind of "improvements" are so minimal it does not matter what way you write it. Anyways, waiting for someone with competence to answer this, I'd like to know too.
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    2. COWhoever voted to reopen should point out why this question is either not a duplicate of what it was closed with or why it should be allowed to co-exist. Also consider flagging it for merging.
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