Hướng dẫn php isset condition
(PHP 4, PHP 5, PHP 7, PHP 8) isset — Determine if a variable is declared and is different than DescriptionIf a variable has been unset with the unset() function, it is no longer considered to be set.
isset() will return If multiple parameters are supplied then isset() will return Parametersvar The variable to be checked. vars Further variables. Return Values Returns ExamplesExample #1 isset() Examples
= '';// This will evaluate to TRUE so the text will be printed. This also work for elements in arrays:
= array ('test' => 1, 'hello' => NULL, 'pie' => array('a' => 'apple'));var_dump(isset($a['test'])); // TRUE Example #2 isset() on String Offsets
The above example will output: bool(false) bool(true) bool(true) bool(true) bool(false) bool(false) NotesWarning isset() only works with variables as passing anything else will result in a parse error. For checking if constants are set use the defined() function.
See Also
p_ignorethis_lbowers at gmail dot com ¶ 5 years ago
kurdtpage at gmail dot com ¶ 5 years ago
a dot schaffhirt at sedna-soft dot de ¶ 13 years ago
beuc at beuc dot net ¶ 15 years ago
yaogzhan at gmail dot com ¶ 17 years ago
__get($p)
ayyappan dot ashok at gmail dot com ¶ 6 years ago
mandos78 AT mail from google ¶ 14 years ago
Cuong Huy To ¶ 11 years ago
true !== array_key_exists('undefined', get_defined_vars())) {echo '$undefined does not exist';} else {echo '$undefined exists';} // '$undefined does not exist'
soywiz at php dot net ¶ 16 years ago
andreasonny83 at gmail dot com ¶ 7 years ago
$var['val1'], $var['val2'] ) && $var['val2'] === 'on' ) { francois vespa ¶ 11 years ago
$array['foo']) || array_key_exists('foo',$array) Andrew Penry ¶ 17 years ago
var_existsHandler($errno, $errstr, $errfile, $errline) { Hayley Watson ¶ 5 years ago
Anl zselgin ¶ 13 years ago
packard_bell_nec at hotmail dot com ¶ 14 years ago
Ashus ¶ 13 years ago
randallgirard at hotmail dot com ¶ 15 years ago
Tee Cee ¶ 16 years ago
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