Question

How to determine if a variable is set and is not NULL in PHP

Answer 1

$var = '';

if (isset($var)) 
    echo "yes";


/*
run: 

yes  

*/

 

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Answer 2

$var = 'PHP';

var_dump(isset($var));


/*
run: 

bool(true)   

*/

 

70+ SQL courses for beginners and professionals

Answer 3

var_dump(isset($var));


/*
run: 

bool(false)   

*/

 

70+ SQL courses for beginners and professionals

Answer 4

$var;

var_dump(isset($var));


/*
run: 

bool(false)   

*/

 

70+ SQL courses for beginners and professionals

Answer 5

$var = "PHP";
var_dump(isset($var));

echo "<br />";
unset($var);
var_dump(isset($var));

/*
run: 

bool(true) 
bool(false) 

*/

 

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Answer 6

$var = null;
var_dump(isset($var));

/*
run: 

bool(false)  

*/

 

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Answer 7

$arr = array('aaa' => 1, 'bbb' => NULL);

echo "<pre>";
var_dump(isset($arr['aaa']));        
var_dump(isset($arr['bbb']));       
var_dump(isset($arr['ccc']));          
echo "</pre>";

/*
run: 

bool(true)
bool(false)
bool(false)

*/

 

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Answer 8

$s = 'PHP Startup or PHP start-up';

echo "<pre>";
var_dump(isset($s['PHP Startup or PHP start-up'])); // false
var_dump(isset($s['PHP'])); // false
var_dump(isset($s[0])); // true
var_dump(isset($s['0'])); // true
var_dump(isset($s[0.7])); // true
var_dump(isset($s['0.7'])); // false
var_dump(isset($s['0 PHP'])); // false
echo "</pre>";

/*
run: 

bool(false)
bool(false)
bool(true)
bool(true)
bool(true)
bool(false)
bool(false)

*/

 

70+ SQL courses for beginners and professionals