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PO
 

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  1. PO
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    <p>If I run the following:</p> <pre><code>echo '&lt;?php echo $foo; ?&gt;' | php </code></pre> <p>I get an error:</p> <pre><code>PHP Notice: Undefined variable: foo in /home/altern8/- on line 1 </code></pre> <p>If I run the following:</p> <pre><code>echo '&lt;?php if ( isset($foo) ) { echo $foo; } ?&gt;' | php </code></pre> <p>I do not get the error. </p> <p>If I have a variable that should be set, I usually do something like the following.</p> <pre><code>$foo = isset($foo) ? $foo : null; </code></pre> <p>or</p> <pre><code>if ( ! isset($foo) ) $foo = null; </code></pre> <p>That way, later in the script, I can safely use $foo and know that it "is set", and that it defaults to null. Later I can <code>if ( is_null($foo) ) { /* ... */ }</code> if I need to and know for certain that the variable exists, even if it is null.</p> <p>The full <a href="http://php.net/manual/en/function.isset.php" rel="nofollow noreferrer">isset documentation</a> reads a little more than just what was initially pasted. Yes, it returns false for a variable that was previously set but is now null, but it also returns false if a variable has not yet been set (ever) and for any variable that has been marked as unset. It also notes that the NULL byte ("\0") is not considered null and will return true.</p> <blockquote> <p>Determine whether a variable is set.</p> <p>If a variable has been unset with unset(), it will no longer be set. isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte ("\0") is not equivalent to the PHP NULL constant.</p> </blockquote>
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    1. POBest way to test for a variable's existence in PHP; isset() is clearly broken
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    1. USBeau Simensen
    1. USBeau Simensen
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    1. COHe got the docs off that link. Read the first sentence, second paragraph of the description section on the link you provided It is exactly what he quoted above.
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      1. USZoredache
    2. COThis isn't a bad practice for simple scripts, but in complex (e.g. large OO) projects, it becomes infeasible. Also, as I said above, is_null() returns TRUE for variables that are not set, so there's really no reason to do what you're saying except to avoid a PHP warning.
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      1. USchazomaticus
    3. COFor well designed "large OO" projects, why would this be a problem at all? Why would you ever have $foo in a method body that may have not been set before its first usage?
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      1. USBeau Simensen
 

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