Anonymous user
Undefined values: Difference between revisions
added php
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Line 24:
undef $var;
# Check to see whether it is defined after we've
# given it an undefined value.
print "var is undefined at third check\n" unless defined $var;
Line 36:
# Because most of the output is conditional, this serves as
# a clear indicator that the
print "Done\n";</lang>
Line 45:
Done
</pre>
=={{header|PHP}}==
<lang php><?php
// Check to see whether it is defined
if (!isset($var))
echo "var is undefined at first check\n";
// Give it a value
$var = "Chocolate";
// Check to see whether it is defined after we gave it the
// value "Chocolate"
if (!isset($var))
echo "var is undefined at second check\n";
// Give the variable an undefined value.
unset($var);
// Check to see whether it is defined after we've explicitly
// given it an undefined value.
if (!isset($var))
echo "var is undefined at third check\n";
// Give the variable a value of 42
$var = 42;
// Check to see whether the it is defined after we've given it
// the value 42.
if (!isset($var))
echo "var is undefined at fourth check\n";
// Because most of the output is conditional, this serves as
// a clear indicator that the program has run to completion.
echo "Done\n";
?></lang>
Results in:
<pre>var is undefined at first check
var is undefined at third check
Done
</pre>
{{omit from|Java|everything is null or defined}}
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